Photoacid generators, chemically amplified resist compositions, and patterning process

ABSTRACT

A photoacid generator has formula (1) wherein R is H, F, Cl, nitro, alkyl or alkoxy, n is 0 or 1, m is 1 or 2, r is an integer of 0-4, and r′ is an integer of 0-5. A chemically amplified resist composition comprising the photoacid generator has advantages including a high resolution, focus latitude, long-term PED dimensional stability, and a satisfactory pattern profile shape. When the photoacid generator is combined with a resin having acid labile groups other than those of the acetal type, resolution and top loss are improved. The composition is suited for deep UV lithography.

CROSS-REFERENCE TO RELATED APPLICATION

This non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application No. 2006-160575 filed in Japan on Jun. 9, 2006, the entire contents of which are hereby incorporated by reference.

TECHNICAL FIELD

This invention relates to photoacid generators for chemically amplified resist compositions, chemically amplified resist compositions comprising the photoacid generators, and a patterning process using the same. The chemically amplified resist compositions are sensitive to such radiation as UV, deep UV, electron beams, x-rays, excimer laser beams, γ-rays, and synchrotron radiation and suitable for the microfabrication of integrated circuits.

BACKGROUND OF THE INVENTION

While a number of efforts are currently being made to achieve a finer pattern rule in the drive for higher integration and operating speeds in LSI devices, deep-ultraviolet lithography is thought to hold particular promise as the next generation in microfabrication technology.

One technology that has attracted a good deal of attention recently utilizes as the deep UV light source a high-intensity KrF excimer laser and an ArF excimer laser of a shorter wavelength. There is a desire to have a microfabrication technique of finer definition by combining exposure light of shorter wavelength with a resist material having a higher resolution.

In this regard, the recently developed, acid-catalyzed, chemical amplification type resist materials are expected to comply with the deep UV lithography because of their many advantages including high sensitivity, resolution and dry etching resistance. The chemically amplified resist materials include positive working materials that leave the unexposed areas with the exposed areas removed and negative working materials that leave the exposed areas with the unexposed areas removed.

In a chemically amplified positive resist composition to be developed with an alkaline developer, a resin and/or compound in which an alkali-soluble phenol or carboxylic acid is partially or entirely protected with acid labile protective groups (commonly referred to as “acid labile groups”) is catalytically decomposed with the acid generated upon exposure, to generate the phenol or carboxylic acid in exposed areas, whereupon the exposed areas are removed with the alkaline developer. In a similar negative resist composition, a resin and/or compound having an alkali-soluble phenol or carboxylic acid and a compound capable of bonding or crosslinking said resin or compound under the action of an acid (referred to as “acid crosslinker”) are crosslinked with the acid generated upon exposure, to render exposed areas insoluble in an alkaline developer, whereupon unexposed areas are removed with the alkaline developer.

On use of the chemically amplified positive resist composition, a resist film is formed by dissolving a resin having acid labile groups as a binder and a compound capable of generating an acid upon exposure to radiation (referred to as “photoacid generator”) in a solvent, applying the resist solution onto a substrate by a variety of methods, and evaporating off the solvent optionally by heating. The resist film is then exposed to radiation, for example, deep UV through a mask of a predetermined pattern. This is optionally followed by post-exposure baking (PEB) for promoting acid-catalyzed reaction. The exposed resist film is developed with an aqueous alkaline developer for removing the exposed areas of the resist film, obtaining a positive pattern profile. The substrate is then etched by any desired technique. Finally the remaining resist film is removed by dissolution in a remover solution or ashing, leaving the substrate having the desired pattern profile.

The chemically amplified positive resist composition adapted for KrF excimer lasers generally uses a phenolic resin, for example, polyhydroxystyrene in which some or all of the hydrogen atoms of phenolic hydroxyl groups are protected with acid labile protective groups. Iodonium salts, sulfonium salts, bissulfonyldiazomethane compounds, N-sulfonyloxydicarboxyimide compounds and O-arenesulfonyloxime compounds are typically used as the photoacid generator. If necessary, there are added additives, for example, a dissolution inhibiting or promoting compound in the form of a carboxylic acid and/or phenol derivative having a molecular weight of up to 3,000 in which some or all of the hydrogen atoms of carboxylic acid and/or phenolic hydroxyl groups are protected with acid labile groups, a carboxylic acid compound for improving dissolution characteristics, a basic compound for improving contrast, and a surfactant for improving coating characteristics.

The photoacid generators in the form of O-arenesulfonyloxime compounds as shown below have a satisfactory sensitivity and resolution and are free of such drawbacks as poor compatibility with resins and low solubility in resist solvents as found with other photoacid generators like sulfonium salts and iodonium salts. They are advantageously used as the photoacid generators in chemically amplified resist compositions, especially chemically amplified positive resist compositions adapted for KrF excimer laser. See U.S. Pat. No. 6,004,724 and JP-A 2004-4614.

As the requisite pattern size is reduced, however, even the use of resist compositions having these photoacid generators combined with the existing acid labile group-bearing resins encounters problems including a poor resolution and a failure to form a satisfactory pattern profile on highly reflective substrate.

For resolution improvement, it is a practice to use more acid labile groups, typically more acid labile acetal groups. However, the reduction of pattern size invites a tendency of reducing the thickness of resist film as well. When a phenolic resin having acid labile groups of acetal type is used, the resist surface becomes more dissolvable. The dissolution of the resist pattern at the top raises problems including a top loss that the pattern profile shape is rounded at the top, or in the case of a contact hole pattern, a failure to form a satisfactory pattern shape due to a lowering of side robe margin (dissolution by a trace amount of leakage or interference light to unexposed areas). When the resist is applied onto inorganic substrates such as SiON substrates which are highly reflective substrates, there arises a problem that standing waves prevent formation of a satisfactory pattern shape. One approach for avoiding these problems is to use resins having acid labile groups of tertiary ether or tertiary ester type which are less labile than the acid labile groups of acetal type. This approach is successful in reducing the top loss, but still fails to form a rectangular micro-pattern and is low in resolution.

For micropatterning purposes, it is also a practice to add the step of changing the shape of a resist pattern after its formation through exposure and development. Exemplary methods include a “thermal flow” method of heating the resist pattern at a temperature equal to or higher than the glass transition temperature to fluidize the resist film for thereby reducing the hole size, and a “chemical shrink” method of forming a pattern profile, applying thereto a material capable of reacting with the resist surface (chemically shrinkable material), heating or whole exposure to bond the shrinkable material to the resist pattern sidewall for thereby reducing the space size.

When it is desired to apply the thermal flow method, some acid generators can be pyrolyzed during heating, making it difficult to control the flow. This propensity manifests, for example, when a photoacid generator having a relatively low pyrolysis temperature is contained in a noticeable amount.

Under these circumstances, U.S. Pat. No. 6,004,724 describes an O-oximesulfonate compound which generates tosyloxybenzene-sulfonic acid upon light exposure. The use of these compounds is still unsatisfactory in forming a resist pattern with a reduced feature size from a thin resist film.

The photoacid generator for use in resist compositions is required to have a fully high solubility (or compatibility) in resist solvents and resins, good storage stability, non-toxicity, ease of application, pattern profile shape, PED stability, high resolution, wide focal depth, and high sensitivity. Prior art photoacid generators, especially O-arenesulfonyloxime compound photoacid generators do not satisfy all these requirements.

In the recent stage when the pattern feature of integrated circuits becomes more miniaturized, more stringent requirements are imposed on the problem of high resolution accompanied with a resist thickness reduction.

DISCLOSURE OF THE INVENTION

An object of the invention is to provide a photoacid generator used to formulate a chemically amplified resist composition which is improved in the control of pattern profile shape, thermal flow and other parameters particularly when the thickness of resist film is reduced; a resist composition comprising the same; and a patterning process.

We have found that a chemically amplified resist composition comprising an O-arenesulfonyloxime compound of the general formula (1), especially formula (1a), shown below, possesses a number of great advantages including dissolution, storage stability, effective coating, minimized line width variation or shape degradation during long-term PED, good pattern profile shape particularly at reduced film thickness, and a high resolution enough for microfabrication, particularly when processed by deep UV lithography.

The present invention provides a photoacid generator, a chemically amplified resist composition comprising the same, and a patterning process, as defined below.

[1] A photoacid generator for use in chemically amplified resist compositions, having the general formula (1):

wherein R is independently selected from the class consisting of hydrogen, fluorine, chlorine atoms, nitro groups, and substituted or unsubstituted, straight, branched or cyclic alkyl and alkoxy groups of 1 to 12 carbon atoms, n is 0 or l, m is 1 or 2, r is an integer of 0 to 4, and r′ is an integer of 0 to 5.

[2] A photoacid generator for use in chemically amplified resist compositions, having the formula (1a).

[3] A chemically amplified resist composition comprising

(A) a resin which changes its solubility in an alkaline developer under the action of an acid, and

(B) the photoacid generator of [1] or [2].

[4] A chemically amplified positive resist composition comprising

(A) a resin which changes its solubility in an alkaline developer under the action of an acid, and

(B) the photoacid generator of [1] or [2].

[5] The resist composition of [3] or [4], further comprising (C) a compound capable of generating an acid upon exposure to radiation, other than component (B). [6] The resist composition of [3] or [4] wherein the resin (A) has such substituent groups having C—O—C linkages that the solubility in an alkaline developer changes as a result of scission of the C—O—C linkages under the action of an acid.

[7] The resist composition of [6] wherein the resin (A) is a polymer containing phenolic hydroxyl groups in which hydrogen atoms of the phenolic hydroxyl groups are substituted with acid labile groups of one or more types in a proportion of more than 0 mol % to 80 mol % on the average of the entire hydrogen atoms of the phenolic hydroxyl groups, the polymer having a weight average molecular weight of 3,000 to 100,000.

[8] The resist composition of [6] wherein the resin (A) is a polymer comprising recurring units of the following general formula (2a):

wherein R¹ is hydrogen or methyl, R² is a straight, branched or cyclic alkyl group of 1 to 8 carbon atoms, x is 0 or a positive integer, y is a positive integer, satisfying x+y≦5, R³ is an acid labile group, S and T are positive integers, satisfying 0<T/(S+T)≦0.8,

wherein the polymer contains units in which hydrogen atoms of phenolic hydroxyl groups are partially substituted with acid labile groups of one or more types, a proportion of the acid labile group-bearing units is on the average from more than 0 mol % to 80 mol % based on the entire polymer, and the polymer has a weight average molecular weight of 3,000 to 100,000.

[9] The resist composition of [6] wherein the resin (A) is a polymer comprising recurring units of the following general formula (2a′):

wherein R¹ is hydrogen or methyl, R² is a straight, branched or cyclic alkyl group of 1 to 8 carbon atoms, R³ is an acid labile group, R^(3a) is hydrogen or an acid labile group, at least some of R^(3a) being acid labile groups, x is 0 or a positive integer, y is a positive integer, satisfying x+y≦5, M and N are positive integers, L is 0 or a positive integer, satisfying 0<N/(M+N+L)≦0.5 and 0<(N+L)/(M+N+L)≦0.8,

wherein the polymer contains on the average from more than 0 mol % to 50 mol % of those units derived from acrylate and methacrylate, and also contains on the average from more than 0 mol % to 80 mol % of acid labile group-bearing units, based on the entire polymer, and the polymer has a weight average molecular weight of 3,000 to 100,000.

[10] The resist composition of [6] wherein the resin (A) is a polymer comprising recurring units of the following general formula (2a″):

wherein R¹ is hydrogen or methyl, R² is a straight, branched or cyclic alkyl group of 1 to 8 carbon atoms, R³ is an acid labile group, R^(3a) is hydrogen or an acid labile group, at least some of R^(3a) being acid labile groups, x is 0 or a positive integer, y is a positive integer, satisfying x+y≦5, yy is 0 or a positive integer, satisfying x+yy≦4, A and B are positive integers, C, D and E each are 0 or a positive integer, satisfying 0<(B+E)/(A+B+C+D+E)≦0.5 and 0<(C+D+E)/(A+B+C+D+E)≦0.8,

wherein the polymer contains on the average from more than 0 mol % to 50 mol % of those units derived from indene and/or substituted indene, and also contains on the average from more than 0 mol % to 80 mol % of acid labile group-bearing units, based on the entire polymer, and the polymer has a weight average molecular weight of 3,000 to 100,000.

[11] The resist composition of any one of [6] to [10] wherein the acid labile group is a tertiary alkyl group of 4 to 20 carbon atoms or a group of the following general formula (5):

wherein R⁸ is a straight, branched or cyclic alkyl group of 1 to 8 carbon atoms or an aryl group of 6 to 20 carbon atoms which may be substituted, h is 0 or 1, i is 0, 1, 2 or 3, satisfying 2h+i=2 or 3.

[12] The resist composition of any one of [3] to [11], further comprising (D) a basic compound. [13] The resist composition of any one of [3] to [12], further comprising (E) an organic acid derivative. [14] The resist composition of any one of [3] to [13], further comprising (F) an organic solvent which is a propylene glycol alkyl ether acetate, an alkyl lactate or a mixture thereof.

[15] A process for forming a pattern, comprising the steps of:

(i) applying the resist composition of any one of [3] to [14] onto a substrate to form a coating,

(ii) heat treating the coating and exposing the coating to high energy radiation with a wavelength of up to 300 nm or electron beam through a photomask,

(iii) optionally heat treating the exposed coating, and developing the coating with a developer.

[16] A process for forming a pattern, comprising the steps of:

(i) applying the resist composition of any one of [3] to [14] onto an inorganic substrate such as a SiON film to form a coating,

(ii) heat treating the coating and exposing the coating to high energy radiation with a wavelength of up to 300 nm or electron beam through a photomask,

(iii) optionally heat treating the exposed coating, and developing the coating with a developer.

[17] A process for forming a pattern, comprising the steps of:

(i) applying the resist composition of any one of [3] to [14] onto a substrate to form a coating,

(ii) heat treating the coating and exposing the coating to high energy radiation with a wavelength of up to 300 nm or electron beam through a photomask,

(iii) optionally heat treating the exposed coating, and developing the coating with a developer to form a pattern profile, and

(iv) heat treating for causing the pattern profile to flow for thereby reducing its size.

BENEFITS OF THE INVENTION

The chemically amplified resist composition comprising a photoacid generator capable of generating an acid upon exposure to actinic radiation according to the invention has many advantages including dissolution, focus latitude, minimized line width variation or shape degradation even on long-term PED, a satisfactory pattern profile shape after development, and a high resolution enough for microfabrication. Particularly when the photoacid generator is combined with a resin having acid labile groups other than those of the acetal type, a high resolution is achieved and the resist shape is improved because the dissolution of resist film top portion in unexposed areas is restrained. The composition is thus suited for microfabrication, especially by deep UV lithography.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Photoacid Generator

In the first embodiment, the invention provides a photoacid generator having an arenesulfonyloxyarenesulfonyl group for use in chemically amplified resist compositions, represented by the general formula (1) or formula (1a).

Herein R is independently selected from among a hydrogen atom, fluorine atom, chlorine atom, nitro group, and a substituted or unsubstituted, straight, branched or cyclic alkyl or alkoxy group of 1 to 12 carbon atoms. The subscript N is 0 or 1, m is 1 or 2, r is an integer of 0 to 4, and r′ is an integer of 0 to 5.

In formula (1), R which may be the same or different stands for a hydrogen atom, a fluorine atom, a chlorine atom, a nitro group, or a substituted or unsubstituted, straight, branched or cyclic alkyl or alkoxy group of 1 to 12 carbon atoms, for example, hydrogen, methyl, ethyl, n-propyl, sec-propyl, cyclopropyl, n-butyl, sec-butyl, iso-butyl, tert-butyl, methoxy, ethoxy, n-propyloxy, sec-propyloxy, n-butyloxy, sec-butyloxy, iso-butyloxy, tert-butyloxy, n-hexyl, n-hexyloxy, n-octyl, n-octyloxy, n-decyl, n-decyloxy, n-dodecyl, and n-dodecyloxy groups. Of these, hydrogen, methyl, ethyl, n-hexyloxy, and n-octyloxy groups are preferred, with hydrogen and methyl being more preferred. The subscript n is 0 or l, m is 1 or 2, r is an integer of 0 to 4, and r′ is an integer of 0 to 5. An arylsulfonyloxy group may substitute on an arenesulfonyl group at any desired position, that is, the substitution position is not particularly limited. In a preferred example, when the arenesulfonyl group is benzenesulfonyl, the preferred substitution position is 4-position; when the arenesulfonyl group is naphthalenesulfonyl, the preferred substitution position differs whether the group is 1- or 2-naphthalenesulfonyl; the preferred substitution position is 4-, 5- or 8-position when the group is 1-naphthalenesulfonyl, and 6-position when the group is 2-naphthalenesulfonyl.

Illustrative examples of (arylsulfonyloxy)arenesulfonyloxy group include, but are not limited to, 4-(4′-toluenesulfonyloxy)benzenesulfonyloxy, 4-(benzenesulfonyloxy)benzenesulfonyloxy, 4-(4′-methoxybenzenesulfonyloxy)benzenesulfonyloxy, 4-(4′-fluorobenzenesulfonyloxy)benzenesulfonyloxy, 4-(4′-trifluoromethylbenzenesulfonyloxy)benzenesulfonyloxy, 4-(pentafluorobenzenesulfonyloxy)benzenesulfonyloxy, 4-(2-naphthalenesulfonyloxy)benzenesulfonyloxy, 3-methoxy-4-(4′-toluenesulfonyloxy)benzenesulfonyloxy, 3-methyl-4-(4′-toluenesulfonyloxy)benzenesulfonyloxy, 2-(4′-toluenesulfonyloxy)naphthalene-6-sulfonyloxy, 1-(4′-toluenesulfonyloxy)naphthalene-4-sulfonyloxy, 1-(4′-toluenesulfonyloxy)naphthalene-8-sulfonyloxy, 2,5-bis(4′-toluenesulfonyloxy)benzenesulfonyloxy, and 2,5-bis(4′-methoxybenzenesulfonyloxy)benzenesulfonyloxy.

The O-arenesulfonyloxime compound of formula (1) or (1a) has an oxime skeleton which can be synthesized by reacting a substituted phenylacetonitrile compound with 2-nitrothiophene in an alcohol solvent under basic conditions. The sulfonic acid moiety can be synthesized by the following method although the synthesis method is not limited thereto.

The (arylsulfonyloxy)arenesulfonic acid can be synthesized according to the teaching of JP-A 2001-122850. Specifically sodium (arylsulfonyloxy)arenesulfonate or the like is obtainable by reacting a hydroxyarenesulfonic acid or hydroxyarenesulfonic acid salt with an arenesulfonyl halide or arenesulfonic acid anhydride in the presence of a base such as sodium hydroxide or potassium hydroxide.

Suitable examples of the hydroxyarenesulfonic acid include, but are not limited to, 4-phenolsulfonic acid, 3-methyl-4-phenolsulfonic acid, 3-methoxy-4-phenolsulfonic acid, 3-nitro-4-phenolsulfonic acid, hydroquinone-2-sulfonic acid, 1,4-naphtholsulfonic acid, 1,5-naphtholsulfonic acid, 2,6-naphtholsulfonic acid, 1,8-naphtholsulfonic acid, 6,7-dihydroxy-2-naphthalenesulfonic acid, and 5,7-dinitro-8-hydroxy-2-naphthalenesulfonic acid. Suitable examples of the arylsulfonyl halide include, but are not limited to, benzenesulfonyl chloride, 4-toluenesulfonyl chloride, 4-ethylbenzenesulfonyl chloride, 4-methoxybenzenesulfonyl chloride, 4-fluorobenzenesulfonyl chloride, 4-trifluoromethylbenzenesulfonyl chloride, 2,4,6-trimethylbenzenesulfonyl chloride, pentafluorobenzenesulfonyl chloride, and 2-naphthalenesulfonyl chloride.

Further the resulting sulfonic acid or sulfonic acid salt is converted into a sulfonyl halide using phosphorus pentachloride or thionyl chloride. For the synthesis of sulfonyl chloride from sulfonic acid salt, reference should be made to the synthesis method described in the above-cited JP-A 2004-4614.

The target O-sulfonyloxime compound is preferably prepared by dissolving an oxime compound and a corresponding sulfonyl halide or sulfonic acid anhydride in a solvent such as THF or CH₂Cl₂, and effecting reaction under basic conditions. Also preferably, the reaction may be effected in a basic solvent such as pyridine.

The substituent group on the O-arenesulfonyloxime compound having formula (1) is as defined above. Preferred examples of the arenesulfonyl moiety are shown below, but not limited thereto.

Resist Composition

In the second embodiment, the present invention provides a chemically amplified resist composition comprising a photoacid generator of the formula (1) or (1a), the composition being sensitive to such radiation as ultraviolet radiation, deep ultraviolet radiation, electron beams, x-rays, excimer laser beams, gamma-rays or synchrotron radiation and suitable for the microfabrication of integrated circuits. The resist composition may be either positive or negative. From the standpoint of resolution and the like, positive resist compositions are more preferred.

The resist compositions of the invention include a variety of embodiments:

1) a chemically amplified positive working resist composition comprising (A) a resin which changes its solubility in an alkaline developer under the action of an acid, (B) the photoacid generator of formula (1) or (1a), and (F) an organic solvent;

2) a chemically amplified positive resist composition of 1) further comprising (C) a photoacid generator capable of generating an acid upon exposure to radiation other than component (B);

3) a chemically amplified positive resist composition of 1) or 2) further comprising (D) a basic compound;

4) a chemically amplified positive resist composition of 1) to 3) further comprising (E) an organic acid derivative; and

5) a chemically amplified positive resist composition of 1) to 4) further comprising (G) a compound with a molecular weight of up to 3,000 which changes its solubility in an alkaline developer under the action of an acid; as well as

6) a chemically amplified negative working resist composition comprising (B) the photoacid generator of formula (1) or (1a), (F) an organic solvent, (H) an alkali-soluble resin, and (I) an acid crosslinker which forms a crosslinked structure under the action of an acid;

7) a chemically amplified negative resist composition of 6) further comprising the above component (C);

8) a chemically amplified negative resist composition of 6) or 7) further comprising the above component (D); and

9) a chemically amplified negative resist composition of 6) to 8) further comprising (J) an alkali-soluble compound having a molecular weight of up to 2,500; but not limited thereto.

Now the respective components are described in detail.

Component (A)

Component (A) is a resin which changes its solubility in an alkaline developer solution under the action of an acid. In the case of chemically amplified positive resist compositions, it is preferably, though not limited thereto, an alkali-soluble resin having phenolic hydroxyl and/or carboxyl groups in which some or all of the phenolic hydroxyl and/or carboxyl groups are protected with acid-labile protective groups having a C—O—C linkage.

The alkali-soluble resins having phenolic hydroxyl and/or carboxyl groups include homopolymers and copolymers of p-hydroxystyrene, m-hydroxystyrene, α-methyl-p-hydroxystyrene, 4-hydroxy-2-methylstyrene, 4-hydroxy-3-methylstyrene, hydroxyindene, methacrylic acid and acrylic acid, and such copolymers having a carboxylic derivative or diphenyl ethylene introduced at their terminus.

Also included are copolymers in which other units are introduced in addition to the above-described units in such a proportion that the solubility in an alkaline developer may not be extremely reduced. Suitable other units are units free of alkali-soluble sites such as units derived from styrene, α-methylstyrene, acrylate, methacrylate, hydrogenated hydroxystyrene, maleic anhydride, maleimide, and substituted or unsubstituted indene. Substituents on the acrylates and methacrylates may be any of the substituents which do not undergo acidolysis. Exemplary substituents are straight, branched or cyclic C₁₋₈ alkyl groups and aromatic groups such as aryl groups, but not limited thereto.

Examples of the alkali-soluble resins or polymers are given below. They may be used as the raw material for the resin (A) which changes its solubility in an alkaline developer solution under the action of an acid or as the alkali-soluble resin (H). Examples include poly(p-hydroxystyrene), poly(m-hydroxystyrene), poly(4-hydroxy-2-methylstyrene), poly(4-hydroxy-3-methylstyrene), poly(α-methyl-p-hydroxystyrene), partially hydrogenated p-hydroxystyrene copolymers, p-hydroxystyrene-α-methyl-p-hydroxystyrene copolymers, p-hydroxystyrene-α-methylstyrene copolymers, p-hydroxystyrene-styrene copolymers, p-hydroxystyrene-m-hydroxystyrene copolymers, p-hydroxystyrene-styrene copolymers, p-hydroxystyrene-indene copolymers, p-hydroxystyrene-acrylic acid copolymers, p-hydroxystyrene-methacrylic acid copolymers, p-hydroxystyrene-methyl acrylate copolymers, p-hydroxystyrene-acrylic acid-methyl methacrylate copolymers, p-hydroxystyrene-methyl methacrylate copolymers, p-hydroxystyrene-methacrylic acid-methyl methacrylate copolymers, poly(methacrylic acid), poly(acrylic acid), acrylic acid-methyl acrylate copolymers, methacrylic acid-methyl methacrylate copolymers, acrylic acid-maleimide copolymers, methacrylic acid-maleimide copolymers, p-hydroxystyrene-acrylic acid-maleimide copolymers, and p-hydroxystyrene-methacrylic acid-maleimide copolymers, but are not limited to these combinations.

Preferred are poly(p-hydroxystyrene), partially hydrogenated p-hydroxystyrene copolymers, p-hydroxystyrene-styrene copolymers, p-hydroxystyrene-indene copolymers, p-hydroxystyrene-acrylic acid copolymers, and p-hydroxystyrene-methacrylic acid copolymers.

Alkali-soluble resins comprising recurring units of the following formula (2), (2′) or (2″) are especially preferred.

Herein R¹ is hydrogen or methyl, R² is a straight, branched or cyclic alkyl group of 1 to 8 carbon atoms, x is 0 or a positive integer, y is a positive integer, satisfying x+y≦5, M and N are positive integers, satisfying 0<N/(M+N)≦0.5, yy is 0 or a positive integer, satisfying x+yy≦4, and A and B are positive integers, and C is 0 or a positive integer, satisfying 0<B/(A+B+C)≦0.5.

The polymer of formula (2″) can be synthesized, for example, by effecting thermal polymerization of an acetoxystyrene monomer, a tertiary alkyl (meth)acrylate monomer and an indene monomer in an organic solvent in the presence of a radical initiator, and subjecting the resulting polymer to alkaline hydrolysis in an organic solvent for deprotecting the acetoxy group, for thereby forming a ternary copolymer of hydroxystyrene, tertiary alkyl (meth)acrylate and indene. The organic solvent used during polymerization is exemplified by toluene, benzene, tetrahydrofuran, diethyl ether and dioxane. Exemplary polymerization initiators include 2,2′-azobisisobutyronitrile, 2,2′-azobis(2,4-dimethylvaleronitrile), dimethyl-2,2-azobis(2-methylpropionate), benzoyl peroxide, and lauroyl peroxide. Polymerization is preferably effected while heating at 50 to 80° C. The reaction time is usually about 2 to 100 hours, preferably about 5 to 20 hours. Aqueous ammonia, triethylamine or the like may be used as the base for the alkaline hydrolysis. For the alkaline hydrolysis, the temperature is usually −20° C. to 100° C., preferably 0° C. to 60° C., and the time is about 0.2 to 100 hours, preferably about 0.5 to 20 hours.

Also included are polymers having the dendritic or hyperbranched polymer structure of formula (2′″) below.

Herein ZZ is a divalent organic group selected from among CH₂, CH(OH), CR²(OH), C═O and C(OR²)(OH) or a trivalent organic group represented by —C(OH)═. Subscript F, which may be identical or different, is a positive integer, and H is a positive integer, satisfying 0.001≦H/(H+ F)≦0.1, and XX is 1 or 2. R¹, R², x and y are as defined above.

The dendritic or hyperbranched polymer of phenol derivative can be synthesized by effecting living anion polymerization of a polymerizable monomer such as 4-tert-butoxystyrene and reacting a branching monomer such as chloromethylstyrene as appropriate during the living anion polymerization.

More particularly, living anion polymerization is started using a polymerizable monomer such as 4-tert-butoxystyrene. After a predetermined amount has been polymerized, a branching monomer such as chloromethylstyrene is introduced and reacted with the intermediate. Then the polymerizable monomer such as 4-tert-butoxystyrene and/or the branching monomer such as chloromethylstyrene is added again for polymerization. This operation is repeated many times until a desired dendritic or hyperbranched polymer is obtained. If necessary, the protective groups used to enable living polymerization are deprotected, yielding a dendritic or hyperbranched polymer of phenol derivative.

Examples of the branching monomer are given below.

R¹, R², x and y are as defined above.

Illustrative examples of the dendritic or hyperbranched polymer are those having recurring units of the following approximate formulas (7) to (11).

Herein, broken lines (- - -) represent polymer chains derived from the phenol derivative monomer, and K represents units derived from the branching monomer. The number of broken line segments between K and K is depicted merely for the sake of convenience, independent of the number of recurring units in the polymer chain included between K and K.

The dendritic or hyperbranched polymer of a phenol derivative is prepared by effecting living polymerization of the phenol derivative, reacting with a compound having a polymerizable moiety and a terminating moiety and proceeding further polymerization. By repeating this operation desired times, a dendritic or hyperbranched polymer of phenol derivative can be synthesized. The living polymerization may be effected by any desired technique although living anion polymerization is preferred because of ease of control. For the detail of synthesis, reference is made to JP-A 2000-344836.

The alkali-soluble resins or polymers should preferably have a weight average molecular weight (Mw) of 3,000 to 100,000, as measured by gel permeation chromatography (GPC) versus polystyrene standards. Many polymers with Mw of less than 3,000 do not perform well and are poor in heat resistance and film formation. Many polymers with Mw of more than 100,000 give rise to a problem with respect to dissolution in the resist solvent and developer. The polymer should also preferably have a dispersity (Mw/Mn) of up to 3.5, and more preferably up to 1.5. With a dispersity of more than 3.5, resolution is low in many cases. Although the preparation method is not critical, a poly(p-hydroxystyrene) or similar polymer with a low dispersity or narrow dispersion can be synthesized by living anion polymerization.

In the resist composition of the invention, a resin having such substituent groups with C—O—C linkages (acid labile groups) that the solubility in an alkaline developer changes as a result of scission of the C—O—C linkages under the action of an acid, especially an alkali-soluble resin as mentioned above is preferably used as component (A). Especially preferred is a polymer comprising recurring units of the above formula (2) and containing phenolic hydroxyl groups in which hydrogen atoms of the phenolic hydroxyl groups are substituted with acid labile groups of one or more types in a proportion of more than 0 mol % to 80 mol % on the average of the entire hydrogen atoms of the phenolic hydroxyl group, the polymer having a weight average molecular weight of 3,000 to 100,000.

Also preferred is a polymer comprising recurring units of the above formula (2′), that is, a copolymer comprising p-hydroxystyrene and/or α-methyl-p-hydroxystyrene and acrylic acid and/or methacrylic acid, wherein some of the hydrogen atoms of the carboxyl groups of acrylic acid and/or methacrylic acid are substituted with acid labile groups of one or more types, and the units derived from acrylate and/or methacrylate are contained in a proportion of more than 0 mol % to 50 mol %, on the average, of the copolymer, and wherein some of the hydrogen atoms of the phenolic hydroxyl groups of p-hydroxystyrene and/or α-methyl-p-hydroxystyrene may be substituted with acid labile groups of one or more types. In the preferred copolymer, the units derived from acrylate and/or methacrylate and from p-hydroxystyrene and/or α-methyl-p-hydroxystyrene having acid labile groups substituted thereon are contained in a proportion of more than 0 mol % to 80 mol %, on the average, of the copolymer.

Alternatively, a polymer comprising recurring units of the above formula (2″), that is, a copolymer comprising p-hydroxystyrene and/or α-methyl-p-hydroxystyrene and substituted and/or unsubstituted indene, is preferred wherein some of the hydrogen atoms of the phenolic hydroxyl groups on p-hydroxystyrene and/or α-methyl-p-hydroxystyrene are substituted with acid labile groups of one or more types, and/or some of the hydrogen atoms of the carboxyl groups on acrylic acid and/or methacrylic acid are substituted with acid labile groups of one or more types. Where the substituted indene has hydroxyl groups, some of the hydrogen atoms of these hydroxyl groups may be substituted with acid labile groups of one or more types. In the preferred copolymer, the units derived from p-hydroxystyrene and/or α-methyl-p-hydroxystyrene having acid labile groups substituted thereon, the units derived from acrylic acid and/or methacrylic acid having acid labile groups substituted thereon, and the units derived from indene having acid labile groups substituted thereon are contained in a proportion of more than 0 mol % to 80 mol %, on the average, of the copolymer.

Exemplary and preferred such polymers are polymers or high molecular weight compounds comprising recurring units represented by the following general formula (2a), (2a′) or (2a″) and having a weight average molecular weight of 3,000 to 100,000.

Herein, R¹ is hydrogen or methyl. R² is a straight, branched or cyclic alkyl group of 1 to 8 carbon atoms. Letter x is 0 or a positive integer, and y is a positive integer, satisfying x+y≦5. R³ is an acid labile group. S and T are positive integers, satisfying 0<T/(S+T)≦ 0.8. R^(3a) is hydrogen or an acid labile group, at least some of the R^(3a) groups are acid labile groups. M and N are positive integers, L is 0 or a positive integer, satisfying 0<N/(M+N+L)≦0.5 and 0<(N+L)/(M+N+L)≦ 0.8. The letter yy is 0 or a positive integer, satisfying x+yy≦4. A and B are positive integers, C, D and E each are 0 or a positive integer, satisfying 0<(B+E)/(A+B+C+D+E)≦0.5 and 0<(C+D+E)/(A+B+C+D+E)≦0.8.

R² stands for straight, branched or cyclic C₁₋₈ alkyl groups, for example, methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, tert-butyl, cyclohexyl and cyclopentyl.

In the event some of phenolic hydroxyl groups or some or all of carboxyl groups on the alkali-soluble resin are protected with acid labile substituent groups represented by C—O—C linkage, the acid labile groups are selected from a variety of such groups. The preferred acid labile groups are groups of the following general formulae (3) to (6), tertiary alkyl groups of 4 to 20 carbon atoms, preferably 4 to 15 carbon atoms, trialkylsilyl groups whose alkyl groups each have 1 to 6 carbon atoms, oxoalkyl groups of 4 to 20 carbon atoms, or aryl-substituted alkyl groups of 7 to 20 carbon atoms. Inter alia, tertiary alkyl groups of 4 to 20 carbon atoms and groups of the following general formula (5) are more preferred.

Herein R⁴ and R⁵ are independently hydrogen or straight, branched or cyclic alkyl groups of 1 to 18 carbon atoms, preferably 1 to 10 carbon atoms, for example, methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, cyclopentyl, cyclohexyl, 2-ethylhexyl and n-octyl. R⁶ is a monovalent hydrocarbon group of 1 to 18 carbon atoms, preferably 1 to 10 carbon atoms, which may have a hetero atom (e.g., oxygen atom), for example, straight, branched or cyclic alkyl groups, and such groups in which some hydrogen atoms are substituted with hydroxyl, alkoxy, oxo, amino or alkylamino groups. Illustrative examples of the substituted alkyl groups are given below.

A pair of R⁴ and R⁵, a pair of R⁴ and R⁶, or a pair of R⁵ and R⁶, taken together, may form a ring. Each of R⁴, R⁵ and R⁶ is a straight or branched alkylene group of 1 to 18 carbon atoms, preferably 1 to 10 carbon atoms, when they form a ring.

R⁷ is a tertiary alkyl group of 4 to 20 carbon atoms, preferably 4 to 15 carbon atoms, a trialkylsilyl group whose alkyl groups each have 1 to 6 carbon atoms, an oxoalkyl group of 4 to 20 carbon atoms or a group of formula (3). Exemplary tertiary alkyl groups are tert-butyl, tert-amyl, 1,1-diethylpropyl, 1-ethylcyclopentyl, 1-butylcyclopentyl, 1-ethylcyclohexyl, 1-butylcyclohexyl, 1-ethyl-2-cyclopentenyl, 1-ethyl-2-cyclohexenyl, 2-methyl-2-adamantyl, 2-ethyl-2-adamantyl and 1-adamantyl-1-methylethyl. Exemplary trialkylsilyl groups are trimethylsilyl, triethylsilyl, and dimethyl-tert-butylsilyl. Exemplary oxoalkyl groups are 3-oxocyclohexyl, 4-methyl-2-oxooxan-4-yl, and 5-methyl-5-oxooxolan-4-yl. Letter z is an integer of 0 to 6.

R⁸ is a straight, branched or cyclic alkyl group of 1 to 8 carbon atoms or substituted or unsubstituted aryl group of 6 to 20 carbon atoms. Exemplary straight, branched or cyclic alkyl groups include methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, tert-amyl, n-pentyl, n-hexyl, cyclopentyl, cyclohexyl, cyclopentylmethyl, cyclopentylethyl, cyclohexylmethyl and cyclohexylethyl. Exemplary substituted or unsubstituted aryl groups include phenyl, methylphenyl, naphthyl, anthryl, phenanthryl, and pyrenyl. Letter h is equal to 0 or 1, i is equal to 0, 1, 2 or 3, satisfying 2h+i=2 or 3.

R⁹ is a straight, branched or cyclic alkyl group of 1 to 8 carbon atoms or substituted or unsubstituted aryl group of 6 to 20 carbon atoms, examples of which are as exemplified for R⁸. R¹⁰ to R¹⁹ are independently hydrogen or monovalent hydrocarbon groups of 1 to 15 carbon atoms which may contain a hetero atom, for example, straight, branched or cyclic alkyl groups such as methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, tert-amyl, n-pentyl, n-hexyl, n-octyl, n-nonyl, n-decyl, cyclopentyl, cyclohexyl, cyclopentylmethyl, cyclopentylethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl, and cyclohexylbutyl, and substituted ones of these groups in which some hydrogen atoms are substituted by hydroxyl, alkoxy, carboxy, alkoxycarbonyl, oxo, amino, alkylamino, cyano, mercapto, alkylthio, and sulfo groups. Any two of R¹⁰ to R¹⁹, for example, a pair of R¹⁰ and R¹¹, a pair of R¹⁰ and R¹², a pair of R¹¹ and R¹³, a pair of R¹² and R¹³, a pair of R¹⁴ and R¹⁵, or a pair of R¹⁶ and R¹⁷, taken together, may form a ring. When any two of R¹⁰ to R¹⁹ form a ring, each is a divalent hydrocarbon group of 1 to 15 carbon atoms which may contain a hetero atom, examples of which are the above-exemplified monovalent hydrocarbon groups with one hydrogen atom eliminated. Also, two of R¹⁰ to R¹⁹ which are attached to adjacent carbon atoms (for example, a pair of R¹⁰ and R¹², a pair of R¹² and R¹⁸, or a pair of R¹⁶ and R¹⁸) may directly bond together to form a double bond.

Of the acid labile groups of formula (3), illustrative examples of the straight or branched groups are given below.

Of the acid labile groups of formula (3), illustrative examples of the cyclic groups include tetrahydrofuran-2-yl, 2-methyltetrahydrofuran-2-yl, tetrahydropyran-2-yl and 2-methyltetrahydropyran-2-yl.

Illustrative examples of the acid labile groups of formula (4) include tert-butoxycarbonyl, tert-butoxycarbonylmethyl, tert-amyloxycarbonyl, tert-amyloxycarbonylmethyl, 1,1-diethylpropyloxycarbonyl, 1,1-diethylpropyloxycarbonylmethyl, 1-ethylcyclopentyloxycarbonyl, 1-ethylcyclopentyloxycarbonylmethyl, 1-ethyl-2-cyclopentenyloxycarbonyl, 1-ethyl-2-cyclopentenyloxycarbonylmethyl, 1-ethoxyethoxycarbonylmethyl, 2-tetrahydropyranyloxycarbonylmethyl, and 2-tetrahydrofuranyloxycarbonylmethyl.

Illustrative examples of the acid labile groups of formula (5) include 1-methylcyclopentyl, 1-ethylcyclopentyl, 1-n-propylcyclopentyl, 1-isopropylcyclopentyl, 1-n-butylcyclopentyl, 1-sec-butylcyclopentyl, 1-methylcyclohexyl, 1-ethylcyclohexyl, 3-methyl-1-cyclopenten-3-yl, 3-ethyl-1-cyclopenten-3-yl, 3-methyl-1-cyclohexen-3-yl, 3-ethyl-1-cyclohexen-3-yl, and 1-cyclohexyl-cyclopentyl.

Illustrative examples of the acid labile groups of formula (6) are given below.

Exemplary of the tertiary alkyl group of 4 to 20 carbon atoms, preferably 4 to 15 carbon atoms, are tert-butyl, tert-amyl, 1,1-diethylpropyl, 1-ethylcyclopentyl, 1-butylcyclopentyl, 1-ethylcyclohexyl, 1-butylcyclohexyl, 1-ethyl-2-cyclopentenyl, 1-ethyl-2-cyclohexenyl, 2-methyl-2-adamantyl, 2-ethyl-2-adamantyl, 1-adamantyl-1-methyl-ethyl.

Exemplary of the trialkylsilyl groups whose alkyl groups each have 1 to 6 carbon atoms are trimethylsilyl, triethylsilyl, and tert-butyldimethylsilyl.

Exemplary of the oxoalkyl groups of 4 to 20 carbon atoms are 3-oxocyclohexyl and groups represented by the following formulae.

Exemplary of the aryl-substituted alkyl groups of 7 to 20 carbon atoms are benzyl, methylbenzyl, dimethylbenzyl, diphenylmethyl, and 1,1-diphenylethyl.

In the resist composition comprising the O-arenesulfonyloxime compound as a photoacid generator, the resin (A) which changes its solubility in an alkaline developer under the action of an acid may also be a polymer of formula (2) or (2′), (2″) or (2′″) in which some of the hydrogen atoms of the phenolic hydroxyl groups are crosslinked within a molecule and/or between molecules, in a proportion of more than 0 mol % to 50 mol %, on the average, of the entire phenolic hydroxyl groups on the polymer, with crosslinking groups having C—O—C linkages represented by the following general formula (12). With respect to illustrative examples and synthesis of polymers crosslinked with acid labile groups, reference should be made to JP-A 11-190904.

Herein, each of R²⁰ and R²¹ is hydrogen or a straight, branched or cyclic alkyl group of 1 to 8 carbon atoms, or R²⁰ and R²¹, taken together, may form a ring, and each of R²⁰ and R²¹ is a straight or branched alkylene group of 1 to 8 carbon atoms when they form a ring. R²² is a straight, branched or cyclic alkylene group of 1 to 10 carbon atoms. Letter “b” is 0 or an integer of 1 to 10. AA is an a-valent aliphatic or alicyclic saturated hydrocarbon group, aromatic hydrocarbon group or heterocyclic group of 1 to 50 carbon atoms, which may be separated by a hetero atom and in which some of the hydrogen atom attached to carbon atoms may be substituted by hydroxyl, carboxyl, carbonyl or halogen. Letter “a” is an integer of 1 to 7, especially 1 to 3.

Preferably in formula (12), R²⁰ is methyl, R²¹ is hydrogen, a is 1, b is 0, and AA is ethylene, 1,4-butylene or 1,4-cyclohexylene.

It is noted that these polymers which are crosslinked within the molecule or between molecules with crosslinking groups having C—O—C linkages can be synthesized by reacting a corresponding non-crosslinked polymer with an alkenyl ether in the presence of an acid catalyst in a conventional manner.

If decomposition of other acid labile groups proceeds under acid catalyst conditions, the end product can be obtained by once reacting the alkenyl ether with hydrochloric acid or the like for conversion to a halogenated alkyl ether and reacting it with the polymer under basic conditions in a conventional manner.

Illustrative, non-limiting, examples of the alkenyl ether include ethylene glycol divinyl ether, triethylene glycol divinyl ether, 1,2-propanediol divinyl ether, 1,3-propanediol divinyl ether, 1,3-butanediol divinyl ether, 1,4-butanediol divinyl ether, neopentyl glycol divinyl ether, trimethylolpropane trivinyl ether, trimethylolethane trivinyl ether, hexanediol divinyl ether, and 1,4-cyclohexanediol divinyl ether.

In the chemically amplified resist composition of the invention, the resin used as component (A) is as described above while the preferred acid labile groups to be substituted for phenolic hydroxyl groups are 1-ethoxyethyl, 1-ethoxypropyl, tetrahydrofuranyl, tetrahydropyranyl, tert-butyl, tert-amyl, 1-ethylcyclohexyloxycarbonylmethyl, tert-butoxycarbonyl, tert-butoxycarbonylmethyl, and substituents of formula (12) wherein R²⁰ is methyl, R²¹ is hydrogen, a is 1, b is 0, and AA is ethylene, 1,4-butylene or 1,4-cyclohexylene. Also preferably, the hydrogen atoms of carboxyl groups on methacrylic acid or acrylic acid are protected with substituent groups as typified by tert-butyl, tert-amyl, 2-methyl-2-adamantyl, 2-ethyl-2-adamantyl, 1-ethylcyclopentyl, 1-ethylcyclohexyl, 1-cyclohexylcyclopentyl, 1-ethylnorbornyl, tetrahydrofuranyl and tetrahydropyranyl.

In a single polymer, these substituents may be incorporated alone or in admixture of two or more types. A blend of two or more polymers having substituents of different types is also acceptable.

The percent proportion of these substituents substituting for phenol and carboxyl groups in the polymer is not critical. Preferably the percent substitution is selected such that when a resist composition comprising the polymer is applied onto a substrate to form a coating, the unexposed area of the coating may have a dissolution rate of 0.01 to 10 Å/sec in a 2.38% tetramethylammonium hydroxide (TMAH) developer.

On use of a polymer containing a greater proportion of carboxyl groups which can reduce the alkali dissolution rate, the percent substitution must be increased or non-acid-decomposable substituents to be described later must be introduced.

When acid labile groups for intramolecular and/or intermolecular crosslinking are to be introduced, the percent proportion of crosslinking substituents is preferably up to 20 mol %, more preferably up to 10 mol %, on the average, based on the entire recurring units of the polymer. If the percent substitution of crosslinking substituents is too high, crosslinking results in a higher molecular weight which can adversely affect dissolution, stability and resolution. It is also preferred to further introduce another non-crosslinking acid labile group into the crosslinked polymer at a percent substitution of up to 10 mol %, on the average, for adjusting the dissolution rate to fall within the above range.

In the case of poly(p-hydroxystyrene), the optimum percent substitution differs between a substituent having a strong dissolution inhibitory action such as a tert-butoxycarbonyl group and a substituent having a weak dissolution inhibitory action such as an acetal group although the overall percent substitution is preferably 10 to 40 mol %, more preferably 20 to 30 mol %, on the average, based on the entire recurring units of the polymer.

Polymers having such acid labile groups introduced therein should preferably have a weight average molecular weight (Mw) of 3,000 to 100,000, as measured by GPC versus polystyrene standards. With a Mw of less than 3,000, polymers would perform poorly and often lack heat resistance and film formability. Polymers with a Mw of more than 100,000 would be less soluble in a developer and a resist solvent.

Where non-crosslinking acid labile groups are introduced, the polymer should preferably have a dispersity (Mw/Mn) of up to 3.5, preferably up to 1.5. A polymer with a dispersity of more than 3.5 often results in a low resolution. Where crosslinking acid labile groups are introduced, the starting alkali-soluble resin should preferably have a dispersity (Mw/Mn) of up to 1.5, and the dispersity is kept at 3 or lower even after protection with crosslinking acid labile groups. If the dispersity is higher than 3, dissolution, coating, storage stability and/or resolution is often poor.

To impart a certain function, suitable substituent groups may be introduced into some of the phenolic hydroxyl and carboxyl groups on the acid labile group-protected polymer. Exemplary are substituent groups for improving adhesion to the substrate, non-acid-labile groups for adjusting dissolution in an alkali developer, and substituent groups for improving etching resistance. Illustrative, non-limiting, substituent groups include 2-hydroxyethyl, 2-hydroxypropyl, methoxymethyl, methoxycarbonyl, ethoxycarbonyl, methoxycarbonylmethyl, ethoxycarbonylmethyl, 4-methyl-2-oxo-4-oxolanyl, 4-methyl-2-oxo-4-oxanyl, methyl, ethyl, propyl, n-butyl, sec-butyl, acetyl, pivaloyl, adamantyl, isoboronyl, and cyclohexyl.

Notably, the use of acid labile groups other than those of the acetal type is preferred for reducing the top loss at the resist top concomitant with a thickness reduction. Specifically, tertiary ethers and tertiary esters are preferred. For phenolic hydroxyl groups, such substituent groups as tert-butyl, tert-amyl, and 1-ethylcyclohexyloxycarbonylmethyl are preferably used. For hydrogen atoms of the carboxyl group on methacrylic acid or acrylic acid, such substituent groups as tert-butyl, tert-amyl, 2-methyl-2-adamantyl, 2-ethyl-2-adamantyl, 1-ethylcyclopentyl, 1-ethylcyclohexyl, 1-cyclohexylcyclopentyl, and 1-ethylnorbornyl are desirable. Protection with these substituent groups is desired.

In the resist composition of the invention, the above-described resin is added in any desired amount, and usually 65 to 99 parts by weight, preferably 65 to 98 parts by weight among 100 parts by weight of the solids in the composition. The term “solids” is used to encompass all components in the resist composition excluding the solvent.

With respect to component (B), illustrative examples of the photoacid generators of formulae (1) or (1a) are as described above.

In the chemically amplified resist composition, an appropriate amount of the photoacid generator added is from 0.1 part to 10 parts by weight, and preferably from 1 to 5 parts by weight, among 100 parts by weight of the solids in the composition. A less amount of the photoacid generator below the range fails to generate a sufficient amount of acid to deprotect acid labile groups in the polymer. Too large amounts may excessively reduce the transmittance of resist film, failing to form a rectangular pattern, and give rise to problems of abnormal particles and deposits during resist storage. The photoacid generators may be used alone or in admixture of two or more.

Component (C)

In one preferred embodiment, the resist composition further contains (C) a compound capable of generating an acid upon exposure to high-energy radiation (UV, deep UV, electron beams, x-rays, excimer laser beams, gamma-rays or synchrotron radiation), that is, a second photoacid generator other than component (B). Suitable second photoacid generators include sulfonium salts, iodonium salts, sulfonyldiazomethane and N-sulfonyloxydicarboxylmide photoacid generators. Exemplary second photoacid generators are given below while they may be used alone or in admixture of two or more.

Sulfonium salts are salts of sulfonium cations with sulfonates, bis(substituted alkylsulfonyl)imides and tris(substituted alkylsulfonyl)methides. Exemplary sulfonium cations include triphenylsulfonium, (4-tert-butoxyphenyl)diphenylsulfonium, bis(4-tert-butoxyphenyl)phenylsulfonium, tris(4-tert-butoxyphenyl)sulfonium, (3-tert-butoxyphenyl)diphenylsulfonium, bis(3-tert-butoxyphenyl)phenylsulfonium, tris(3-tert-butoxyphenyl)sulfonium, (3,4-di-tert-butoxyphenyl)diphenylsulfonium, bis(3,4-di-tert-butoxyphenyl)phenylsulfonium, tris(3,4-di-tert-butoxyphenyl)sulfonium, diphenyl(4-thiophenoxyphenyl)sulfonium, (4-tert-butoxycarbonylmethyloxyphenyl)diphenylsulfonium, tris(4-tert-butoxycarbonylmethyloxyphenyl)sulfonium, (4-tert-butoxyphenyl)bis(4-dimethylaminophenyl)sulfonium, tris(4-dimethylaminophenyl)sulfonium, 4-methylphenyldiphenylsulfonium, 4-tert-butylphenyldiphenylsulfonium, bis(4-methylphenyl)phenylsulfonium, bis(4-tert-butylphenyl)phenylsulfonium, tris(4-methylphenyl)sulfonium, tris(4-tert-butylphenyl)sulfonium, tris(phenylmethyl)sulfonium, 2-naphthyldiphenylsulfonium, dimethyl-2-naphthylsulfonium, 4-hydroxyphenyldimethylsulfonium, 4-methoxyphenyldimethylsulfonium, trimethylsulfonium, 2-oxocyclohexylcyclohexylmethylsulfonium, trinaphthylsulfonium, tribenzylsulfonium, diphenylmethylsulfonium, dimethylphenylsulfonium, 2-oxopropylthiacyclopentanium, 2-oxobutylthiacyclopentanium, 2-oxo-3,3-dimethylbutylthiacyclopentanium, 2-oxo-2-phenylethylthiacyclopentanium, 4-n-butoxynaphthyl-1-thiacyclopentanium, and 2-n-butoxynaphthyl-1-thiacyclopentanium. Exemplary sulfonates include trifluoromethanesulfonate, pentafluoroethanesulfonate, heptafluoropropanesulfonate, nonafluorobutanesulfonate, dodecafluorohexanesulfonate, pentafluoroethylperfluorocyclohexanesulfonate, heptadecafluorooctanesulfonate, perfluoro-4-ethylcyclohexanesulfonate, 2,2,2-trifluoroethanesulfonate, pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate, 4-fluorobenzenesulfonate, mesitylenesulfonate, 2,4,6-triisopropylbenzenesulfonate, toluenesulfonate, benzenesulfonate, 4-(4′-toluenesulfonyloxy)benzenesulfonate, 6-(4-toluenesulfonyloxy)naphthalene-2-sulfonate, 4-(4-toluenesulfonyloxy)naphthalene-1-sulfonate, 5-(4-toluenesulfonyloxy)naphthalene-1-sulfonate, 8-(4-toluenesulfonyloxy)naphthalene-1-sulfonate, naphthalenesulfonate, camphorsulfonate, octanesulfonate, dodecylbenzenesulfonate, butanesulfonate, methanesulfonate, 1,1-difluoro-2-naphthyl-ethanesulfonate, 1,1,2,2-tetrafluoro-2-(norbornan-2-yl)ethanesulfonate, and 1,1,2,2-tetrafluoro-2-(tetracyclo[4.4.0.1^(2,5). 1^(7,10)]dodec-3-en-8-yl)ethanesulfonate. Exemplary bis(substituted alkylsulfonyl)imides include bistrifluoromethylsulfonylimide, bispentafluoroethylsulfonylimide, bisheptafluoropropylsulfonylimide, and 1,3-propylenebissulfonylimide. A typical tris(substituted alkylsulfonyl)methide is tristrifluoromethylsulfonylmethide. Sulfonium salts based on combination of the foregoing examples are included.

Iodonium salts are salts of iodonium cations with sulfonates, bis(substituted alkylsulfonyl)imides and tris(substituted alkylsulfonyl)methides. Exemplary iodonium cations are aryliodonium cations including diphenyliodinium, bis(4-tert-butylphenyl)iodonium, 4-tert-butoxyphenylphenyliodonium, and 4-methoxyphenylphenyliodonium. Exemplary sulfonates include trifluoromethanesulfonate, pentafluoroethanesulfonate, heptafluoropropanesulfonate, nonafluorobutanesulfonate, dodecafluorohexanesulfonate, pentafluoroethylperfluorocyclohexanesulfonate, heptadecafluorooctanesulfonate, perfluoro-4-ethylcyclohexanesulfonate, 2,2,2-trifluoroethanesulfonate, pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate, 4-fluorobenzenesulfonate, mesitylenesulfonate, 2,4,6-triisopropylbenzenesulfonate, toluenesulfonate, benzenesulfonate, 4-(4′-toluenesulfonyloxy)benzenesulfonate, 6-(4-toluenesulfonyloxy)naphthalene-2-sulfonate, 4-(4-toluenesulfonyloxy)naphthalene-1-sulfonate, 5-(4-toluenesulfonyloxy)naphthalene-1-sulfonate, 8-(4-toluenesulfonyloxy)naphthalene-1-sulfonate, naphthalenesulfonate, camphorsulfonate, octanesulfonate, dodecylbenzenesulfonate, butanesulfonate, methanesulfonate, 1,1-difluoro-2-naphthyl-ethanesulfonate, 1,1,2,2-tetrafluoro-2-(norbornan-2-yl)ethanesulfonate, and 1,1,2,2-tetrafluoro-2-(tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-en-8-yl)ethanesulfonate. Exemplary bis(substituted alkylsulfonyl)imides include bistrifluoromethylsulfonylimide, bispentafluoroethylsulfonylimide, bisheptafluoropropylsulfonylimide, and 1,3-propylenebissulfonylimide. A typical tris(substituted alkylsulfonyl)methide is tristrifluoromethylsulfonylmethide. Iodonium salts based on combination of the foregoing examples are included.

Exemplary sulfonyldiazomethane compounds include bissulfonyldiazomethane compounds and sulfonyl-carbonyldiazomethane compounds such as bis(ethylsulfonyl)diazomethane, bis(1-methylpropylsulfonyl)diazomethane, bis(2-methylpropylsulfonyl)diazomethane, bis(1,1-dimethylethylsulfonyl)diazomethane, bis(cyclohexylsulfonyl)diazomethane, bis(perfluoroisopropylsulfonyl)diazomethane, bis(phenylsulfonyl)diazomethane, bis(4-methylphenylsulfonyl)diazomethane, bis(2,4-dimethylphenylsulfonyl)diazomethane, bis(4-acetyloxyphenylsulfonyl)diazomethane, bis(4-methanesulfonyloxyphenylsulfonyl)diazomethane, bis(4-(4-toluenesulfonyloxy)phenylsulfonyl)diazomethane, bis(2-naphthylsulfonyl)diazomethane, 4-methylphenylsulfonylbenzoyldiazomethane, tert-butylcarbonyl-4-methylphenylsulfonyldiazomethane, 2-naphthylsulfonylbenzoyldiazomethane, 4-methylphenylsulfonyl-2-naphthoyldiazomethane, methylsulfonylbenzoyldiazomethane, and tert-butoxycarbonyl-4-methylphenylsulfonyldiazomethane.

N-sulfonyloxyimide photoacid generators include combinations of imide skeletons with sulfonates. Exemplary imide skeletons are succinimide, naphthalenedicarboximide, phthalimide, cyclohexyldicarboximide, 5-norbornene-2,3-dicarboximide, and 7-oxabicyclo[2.2.1]-5-heptene-2,3-dicarboximide. Exemplary sulfonates include trifluoromethanesulfonate, pentafluoroethanesulfonate, heptafluoropropanesulfonate, nonafluorobutanesulfonate, dodecafluorohexanesulfonate, pentafluoroethylperfluorocyclohexanesulfonate, heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate, pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate, 4-fluorobenzenesulfonate, mesitylenesulfonate, 2,4,6-triisopropylbenzenesulfonate, toluenesulfonate, benzenesulfonate, naphthalenesulfonate, camphorsulfonate, octanesulfonate, dodecylbenzenesulfonate, butanesulfonate, methanesulfonate, 1,1-difluoro-2-naphthyl-ethanesulfonate, 1,1,2,2-tetrafluoro-2-(norbornan-2-yl)ethanesulfonate, and 1,1,2,2-tetrafluoro-2-(tetracyclo[4.4.0.1^(2,5). 1^(7,10)]dodec-3-en-8-yl)ethanesulfonate.

Benzoinsulfonate photoacid generators include benzoin tosylate, benzoin mesylate, and benzoin butanesulfonate.

Pyrogallol trisulfonate photoacid generators include pyrogallol, phloroglucinol, catechol, resorcinol, and hydroquinone, in which all the hydroxyl groups are substituted by trifluoromethanesulfonate, pentafluoroethanesulfonate, heptafluoropropanesulfonate, nonafluorobutanesulfonate, dodecafluorohexanesulfonate, pentafluoroethylperfluorocyclohexanesulfonate, heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate, pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate, 4-fluorobenzenesulfonate, toluenesulfonate, benzenesulfonate, naphthalenesulfonate, camphorsulfonate, octanesulfonate, dodecylbenzenesulfonate, butanesulfonate, methanesulfonate, 1,1-difluoro-2-naphthyl-ethanesulfonate, 1,1,2,2-tetrafluoro-2-(norbornan-2-yl)ethanesulfonate, and 1,1,2,2-tetrafluoro-2-(tetracyclo[4.4.0.1^(2,5). 1^(7,10)]dodec-3-en-8-yl)ethanesulfonate.

Nitrobenzyl sulfonate photoacid generators include 2,4-dinitrobenzyl sulfonate, 2-nitrobenzyl sulfonate, and 2,6-dinitrobenzyl sulfonate, with exemplary sulfonates including trifluoromethanesulfonate, pentafluoroethanesulfonate, heptafluoropropanesulfonate, nonafluorobutanesulfonate, dodecafluorohexanesulfonate, pentafluoroethylperfluorocyclohexanesulfonate, heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate, pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate, 4-fluorobenzenesulfonate, toluenesulfonate, benzenesulfonate, naphthalenesulfonate, camphorsulfonate, octanesulfonate, dodecylbenzenesulfonate, butanesulfonate, methanesulfonate, 1,1-difluoro-2-naphthyl-ethanesulfonate, 1,1,2,2-tetrafluoro-2-(norbornan-2-yl)ethanesulfonate, and 1,1,2,2-tetrafluoro-2-(tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-en-8-yl)ethanesulfonate. Also useful are analogous nitrobenzyl sulfonate compounds in which the nitro group on the benzyl side is substituted by a trifluoromethyl group.

Sulfone photoacid generators include bis(phenylsulfonyl)methane, bis(4-methylphenylsulfonyl)methane, bis(2-naphthylsulfonyl)methane, 2,2-bis(phenylsulfonyl)propane, 2,2-bis(4-methylphenylsulfonyl)propane, 2,2-bis(2-naphthylsulfonyl)propane, 2-methyl-2-(p-toluenesulfonyl)propiophenone, 2-cyclohexylcarbonyl-2-(p-toluenesulfonyl)propane, and 2,4-dimethyl-2-(p-toluenesulfonyl)pentan-3-one.

Illustrative of the O-arenesulfonyloxime or O-alkylsulfonyloxime compound (oximesulfonate) are photoacid generators in the form of glyoxime derivatives, typically the compounds described in Japanese Patent No. 2,906,999 and JP-A 9-301948; photoacid generators of oximesulfonate type having a conjugated system extended via thiophene or cyclohexadiene, typically the compounds described in U.S. Pat. No. 6,004,724; oximesulfonate compounds stabilized with electron withdrawing groups such as trifluoromethyl groups, typically the compounds described in U.S. Pat. No. 6,261,738, JP-A 2000-314956, and International Publication 2004/074242; oximesulfonate compounds derived from phenylacetonitrile and substituted acetonitriles, typically the compounds described in JP-A 9-95479, JP-A 9-230588 and the references cited therein; and bisoximesulfonate compounds, typically the compounds described in JP-A 9-208554, GB 2,348,644A, and JP-A 2002-278053.

When the second photoacid generator (C) is added to the resist composition for KrF excimer laser lithography, the preferred photoacid generators are sulfonium salts, bissulfonyldiazomethanes, N-sulfonyloxydicarboximides, and oximesulfonates. Illustrative preferred photoacid generators include triphenylsulfonium p-toluenesulfonate, triphenylsulfonium camphorsulfonate, triphenylsulfonium pentafluorobenzenesulfonate, triphenylsulfonium nonafluorobutanesulfonate, triphenylsulfonium 4-(4′-toluenesulfonyloxy)benzenesulfonate, triphenylsulfonium 2,4,6-triisopropylbenzenesulfonate, 4-tert-butoxyphenyldiphenylsulfonium p-toluenesulfonate, 4-tert-butoxyphenyldiphenylsulfonium camphorsulfonate, 4-tert-butoxyphenyldiphenylsulfonium 4-(4′-toluenesulfonyloxy)benzenesulfonate, tris(4-methylphenyl)sulfonium camphorsulfonate, tris(4-tert-butylphenyl)sulfonium camphorsulfonate, bis(tert-butylsulfonyl)diazomethane, bis(cyclohexylsulfonyl)diazomethane, bis(2,4-dimethylphenylsulfonyl)diazomethane, bis(4-tert-butylphenylsulfonyl)diazomethane, N-camphorsulfonyloxy-5-norbornene-2,3-carboximide, N-p-toluenesulfonyloxy-5-norbornene-2,3-carboximide, (5-(10-camphorsulfonyl)oximino-5H-thiophen-2-ylidene), (2-methylphenyl)acetonitrile, 5-(4-toluenesulfonyl)oximino-5H-thiophen-2-ylidene, and (2-methylphenyl)acetonitrile.

In the resist composition comprising the O-arenesulfonyloxime compound as the first photoacid generator (B) according to the invention, the second photoacid generator (C) may be used in any desired amount as long as it does not compromise the effects of the O-arenesulfonyloxime compound. An appropriate amount of the second photoacid generator (C) is 0 to 10 parts, and especially 0 to 5 parts by weight among 100 parts by weight of the solids in the composition. Too high a proportion of the second photoacid generator (C) may give rise to problems of degraded resolution and foreign matter upon development and resist film peeling. The second photoacid generators may be used alone or in admixture of two or more. The transmittance of the resist film can be controlled by using a (second) photoacid generator having a low transmittance at the exposure wavelength and adjusting the amount of the photoacid generator added.

In the resist composition comprising the O-arenesulfonyloxime compound as the photoacid generator according to the invention, there may be added a compound which is decomposed with an acid to generate another acid, that is, acid-amplifier compound. For these compounds, reference should be made to J. Photopolym. Sci. and Tech., 8, 43-44, 45-46 (1995), and ibid., 9, 29-30 (1996).

Examples of the acid-amplifier compound include tert-butyl-2-methyl-2-tosyloxymethyl acetoacetate and 2-phenyl-2-(2-tosyloxyethyl)-1,3-dioxolane, but are not limited thereto. Of well-known photoacid generators, many of those compounds having poor stability, especially poor thermal stability exhibit an acid amplifier-like behavior.

In the resist composition of the invention, an appropriate amount of the acid-amplifier compound is up to 2 parts, and especially up to 1 part by weight among 100 parts by weight of the solids in the composition. Excessive amounts of the acid-amplifier compound make diffusion control difficult, leading to degradation of resolution and pattern configuration.

Component (D)

The basic compound used as component (D) is preferably a compound capable of suppressing the rate of diffusion when the acid generated by the photoacid generator diffuses within the resist film. The inclusion of this type of basic compound holds down the rate of acid diffusion within the resist film, resulting in better resolution. In addition, it suppresses changes in sensitivity following exposure and reduces substrate and environment dependence, as well as improving the exposure latitude and the pattern profile.

Examples of basic compounds include primary, secondary, and tertiary aliphatic amines, mixed amines, aromatic amines, heterocyclic amines, nitrogen-containing compounds having carboxyl group, nitrogen-containing compounds having sulfonyl group, nitrogen-containing compounds having hydroxyl group, nitrogen-containing compounds having hydroxyphenyl group, alcoholic nitrogen-containing compounds, amide derivatives, and imide derivatives.

Examples of suitable primary aliphatic amines include ammonia, methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine, isobutylamine, sec-butylamine, tert-butylamine, pentylamine, tert-amylamine, cyclopentylamine, hexylamine, cyclohexylamine, heptylamine, octylamine, nonylamine, decylamine, dodecylamine, cetylamine, methylenediamine, ethylenediamine, and tetraethylenepentamine. Examples of suitable secondary aliphatic amines include dimethylamine, diethylamine, di-n-propylamine, diisopropylamine, di-n-butylamine, diisobutylamine, di-sec-butylamine, dipentylamine, dicyclopentylamine, dihexylamine, dicyclohexylamine, diheptylamine, dioctylamine, dinonylamine, didecylamine, didodecylamine, dicetylamine, N,N-dimethylmethylenediamine, N,N-dimethylethylenediamine, and N,N-dimethyltetraethylenepentamine. Examples of suitable tertiary aliphatic amines include trimethylamine, triethylamine, tri-n-propylamine, triisopropylamine, tri-n-butylamine, triisobutylamine, tri-sec-butylamine, tripentylamine, tricyclopentylamine, trihexylamine, tricyclohexylamine, triheptylamine, trioctylamine, trinonylamine, tridecylamine, tridodecylamine, tricetylamine, N,N,N′,N′-tetramethylmethylenediamine, N,N,N′,N′-tetramethylethylenediamine, and N,N,N′,N′-tetramethyltetraethylenepentamine.

Examples of suitable mixed amines include dimethylethylamine, methylethylpropylamine, benzylamine, phenethylamine, and benzyldimethylamine. Examples of suitable aromatic and heterocyclic amines include aniline derivatives (e.g., aniline, N-methylaniline, N-ethylaniline, N-propylaniline, N,N-dimethylaniline, 2-methylaniline, 3-methylaniline, 4-methylaniline, ethylaniline, propylaniline, trimethylaniline, 2-nitroaniline, 3-nitroaniline, 4-nitroaniline, 2,4-dinitroaniline, 2,6-dinitroaniline, 3,5-dinitroaniline, and N,N-dimethyltoluidine), diphenyl(p-tolyl)amine, methyldiphenylamine, triphenylamine, phenylenediamine, naphthylamine, diaminonaphthalene, pyrrole derivatives (e.g., pyrrole, 2H-pyrrole, 1-methylpyrrole, 2,4-dimethylpyrrole, 2,5-dimethylpyrrole, and N-methylpyrrole), oxazole derivatives (e.g., oxazole and isooxazole), thiazole derivatives (e.g., thiazole and isothiazole), imidazole derivatives (e.g., imidazole, 4-methylimidazole, and 4-methyl-2-phenylimidazole), pyrazole derivatives, furazan derivatives, pyrroline derivatives (e.g., pyrroline and 2-methyl-1-pyrroline), pyrrolidine derivatives (e.g., pyrrolidine, N-methylpyrrolidine, pyrrolidinone, and N-methylpyrrolidone), imidazoline derivatives, imidazolidine derivatives, pyridine derivatives (e.g., pyridine, methylpyridine, ethylpyridine, propylpyridine, butylpyridine, 4-(1-butylpentyl)pyridine, dimethylpyridine, trimethylpyridine, triethylpyridine, phenylpyridine, 3-methyl-2-phenylpyridine, 4-tert-butylpyridine, diphenylpyridine, benzylpyridine, methoxypyridine, butoxypyridine, dimethoxypyridine, 1-methyl-2-pyridine, 4-pyrrolidinopyridine, 1-methyl-4-phenylpyridine, 2-(1-ethylpropyl)pyridine, aminopyridine, and dimethylaminopyridine), pyridazine derivatives, pyrimidine derivatives, pyrazine derivatives, pyrazoline derivatives, pyrazolidine derivatives, piperidine derivatives, piperazine derivatives, morpholine derivatives, indole derivatives, isoindole derivatives, 1H-indazole derivatives, indoline derivatives, quinoline derivatives (e.g., quinoline and 3-quinolinecarbonitrile), isoquinoline derivatives, cinnoline derivatives, quinazoline derivatives, quinoxaline derivatives, phthalazine derivatives, purine derivatives, pteridine derivatives, carbazole derivatives, phenanthridine derivatives, acridine derivatives, phenazine derivatives, 1,10-phenanthroline derivatives, adenine derivatives, adenosine derivatives, guanine derivatives, guanosine derivatives, uracil derivatives, and uridine derivatives.

Examples of suitable nitrogen-containing compounds having carboxyl group include aminobenzoic acid, indolecarboxylic acid, and amino acid derivatives (e.g. nicotinic acid, alanine, alginine, aspartic acid, glutamic acid, glycine, histidine, isoleucine, glycylleucine, leucine, methionine, phenylalanine, threonine, lysine, 3-aminopyrazine-2-carboxylic acid, and methoxyalanine). Examples of suitable nitrogen-containing compounds having sulfonyl group include 3-pyridinesulfonic acid and pyridinium p-toluenesulfonate. Examples of suitable nitrogen-containing compounds having hydroxyl group, nitrogen-containing compounds having hydroxyphenyl group, and alcoholic nitrogen-containing compounds include 2-hydroxypyridine, aminocresol, 2,4-quinolinediol, 3-indolemethanol hydrate, monoethanolamine, diethanolamine, triethanolamine, N-ethyldiethanolamine, N,N-diethylethanolamine, triisopropanolamine, 2,2′-iminodiethanol, 2-aminoethanol, 3-amino-1-propanol, 4-amino-1-butanol, 4-(2-hydroxyethyl)morpholine, 2-(2-hydroxyethyl)pyridine, 1-(2-hydroxyethyl)piperazine, 1-[2-(2-hydroxyethoxy)ethyl]piperazine, piperidine ethanol, 1-(2-hydroxyethyl)pyrrolidine, 1-(2-hydroxyethyl)-2-pyrrolidinone, 3-piperidino-1,2-propanediol, 3-pyrrolidino-1,2-propanediol, 8-hydroxyjulolidine, 3-quinuclidinol, 3-tropanol, 1-methyl-2-pyrrolidine ethanol, 1-aziridine ethanol, N-(2-hydroxyethyl)phthalimide, and N-(2-hydroxyethyl)isonicotinamide. Examples of suitable amide derivatives include formamide, N-methylformamide, N,N-dimethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, propionamide, and benzamide. Suitable imide derivatives include phthalimide, succinimide, and maleimide.

In addition, basic compounds of the following general formula (D1) may also be included alone or in admixture.

N(X′)_(w)(Y)_(3-w)  (D1)

In the formula, w is equal to 1, 2 or 3; Y is independently hydrogen or a straight, branched or cyclic alkyl group of 1 to 20 carbon atoms which may contain a hydroxyl group or ether structure; and X′ is independently selected from groups of the following general formulas (X′1) to (X′3), and two or three X′ may bond together to form a ring.

In the formulas, R³⁰⁰, R³⁰² and R³⁰⁵ are independently straight or branched alkylene groups of 1 to 4 carbon at oms; R³⁰¹, R³⁰⁴ and R³⁰⁶ are independently hydrogen, straight, branched or cyclic alkyl groups of 1 to 20 carbon atoms, which may contain at least one hydroxyl group, ether structure, ester structure or lactone ring; and R³⁰³ is a single bond or a straight or branched alkylene group of 1 to 4 carbon atoms.

Illustrative examples of the basic compounds of formula (Dl) include tris(2-methoxymethoxyethyl)amine, tris{2-(2-methoxyethoxy)ethyl}amine, tris{2-(2-methoxyethoxymethoxy)ethyl}amine, tris{2-(1-methoxyethoxy)ethyl}amine, tris{2-(1-ethoxyethoxy)ethyl}amine, tris{2-(1-ethoxypropoxy)ethyl}amine, tris[2-{2-(2-hydroxyethoxy)ethoxy}ethyl]amine, 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane, 4,7,13,18-tetraoxa-1,10-diazabicyclo[8.5.5]eicosane, 1,4,10,13-tetraoxa-7,16-diazabicyclooctadecane, 1-aza-12-crown-4, 1-aza-15-crown-5, 1-aza-18-crown-6, tris(2-formyloxyethyl)amine, tris(2-acetoxyethyl)amine, tris(2-propionyloxyethyl)amine, tris(2-butyryloxyethyl)amine, tris(2-isobutyryloxyethyl)amine, tris(2-valeryloxyethyl)amine, tris(2-pivaloyloxyethyl)amine, N,N-bis(2-acetoxyethyl)-2-(acetoxyacetoxy)ethylamine, tris(2-methoxycarbonyloxyethyl)amine, tris(2-tert-butoxycarbonyloxyethyl)amine, tris[2-(2-oxopropoxy)ethyl]amine, tris[2-(methoxycarbonylmethyl)oxyethyl]amine, tris[2-(tert-butoxycarbonylmethyloxy)ethyl]amine, tris[2-(cyclohexyloxycarbonylmethyloxy)ethyl]amine, tris(2-methoxycarbonylethyl)amine, tris(2-ethoxycarbonylethyl)amine, N,N-bis(2-hydroxyethyl)-2-(methoxycarbonyl)ethylamine, N,N-bis(2-acetoxyethyl)-2-(methoxycarbonyl)ethylamine, N,N-bis(2-hydroxyethyl)-2-(ethoxycarbonyl)ethylamine, N,N-bis(2-acetoxyethyl)-2-(ethoxycarbonyl)ethylamine, N,N-bis(2-hydroxyethyl)-2-(2-methoxyethoxycarbonyl)ethylamine, N,N-bis(2-acetoxyethyl)-2-(2-methoxyethoxycarbonyl)ethylamine, N,N-bis(2-hydroxyethyl)-2-(2-hydroxyethoxycarbonyl)ethylamine, N,N-bis(2-acetoxyethyl)-2-(2-acetoxyethoxycarbonyl)ethylamine, N,N-bis(2-hydroxyethyl)-2-[(methoxycarbonyl)methoxycarbonyl]-ethylamine, N,N-bis(2-acetoxyethyl)-2-[(methoxycarbonyl)methoxycarbonyl]-ethylamine, N,N-bis(2-hydroxyethyl)-2-(2-oxopropoxycarbonyl)ethylamine, N,N-bis(2-acetoxyethyl)-2-(2-oxopropoxycarbonyl)ethylamine, N,N-bis(2-hydroxyethyl)-2-(tetrahydrofurfuryloxycarbonyl)ethylamine, N,N-bis(2-acetoxyethyl)-2-(tetrahydrofurfuryloxycarbonyl)ethylamine, N,N-bis(2-hydroxyethyl)-2-[(2-oxotetrahydrofuran-3-yl)oxy-carbonyl]ethylamine, N,N-bis(2-acetoxyethyl)-2-[(2-oxotetrahydrofuran-3-yl)oxy-carbonyl]ethylamine, N,N-bis(2-hydroxyethyl)-2-(4-hydroxybutoxycarbonyl)ethylamine, N,N-bis(2-formyloxyethyl)-2-(4-formyloxybutoxycarbonyl)ethylamine, N,N-bis(2-formyloxyethyl)-2-(2-formyloxyethoxycarbonyl)ethylamine, N,N-bis(2-methoxyethyl)-2-(methoxycarbonyl)ethylamine, N-(2-hydroxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine, N-(2-acetoxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine, N-(2-hydroxyethyl)-bis[2-(ethoxycarbonyl)ethyl]amine, N-(2-acetoxyethyl)-bis[2-(ethoxycarbonyl)ethyl]amine, N-(3-hydroxy-1-propyl)-bis[2-(methoxycarbonyl)ethyl]amine, N-(3-acetoxy-1-propyl)-bis[2-(methoxycarbonyl)ethyl]amine, N-(2-methoxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine, N-butyl-bis[2-(methoxycarbonyl)ethyl]amine, N-butyl-bis[2-(2-methoxyethoxycarbonyl)ethyl]amine, N-methyl-bis(2-acetoxyethyl)amine, N-ethyl-bis(2-acetoxyethyl)amine, N-methyl-bis(2-pivaloyloxyethyl)amine, N-ethyl-bis[2-(methoxycarbonyloxy)ethyl]amine, N-ethyl-bis[2-(tert-butoxycarbonyloxy)ethyl]amine, tris(methoxycarbonylmethyl)amine, tris(ethoxycarbonylmethyl)amine, N-butyl-bis(methoxycarbonylmethyl)amine, N-hexyl-bis(methoxycarbonylmethyl)amine, and β-(diethylamino)-δ-valerolactone.

Also useful are one or more of cyclic structure-bearing basic compounds having the following general formula (D2).

Herein X′ is as defined above, and R³⁰⁷ is a straight or branched alkylene group of 2 to 20 carbon atoms which may contain one or more carbonyl groups, ether structures, ester structures or sulfide structures.

Illustrative examples of the cyclic structure-bearing basic compounds having formula (D2) include 1-[2-(methoxymethoxy)ethyl]pyrrolidine, 1-[2-(methoxymethoxy)ethyl]piperidine, 4-[2-(methoxymethoxy)ethyl]morpholine, 1-[2-[(2-methoxyethoxy)methoxy]ethyl]pyrrolidine, 1-[2-[(2-methoxyethoxy)methoxy]ethyl]piperidine, 4-[2-[(2-methoxyethoxy)methoxy]ethyl]morpholine, 2-(1-pyrrolidinyl)ethyl acetate, 2-piperidinoethyl acetate, 2-morpholinoethyl acetate, 2-(1-pyrrolidinyl)ethyl formate, 2-piperidinoethyl propionate, 2-morpholinoethyl acetoxyacetate, 2-(1-pyrrolidinyl)ethyl methoxyacetate, 4-[2-(methoxycarbonyloxy)ethyl]morpholine, 1-[2-(t-butoxycarbonyloxy)ethyl]piperidine, 4-[2-(2-methoxyethoxycarbonyloxy)ethyl]morpholine, methyl 3-(1-pyrrolidinyl)propionate, methyl 3-piperidinopropionate, methyl 3-morpholinopropionate, methyl 3-(thiomorpholino)propionate, methyl 2-methyl-3-(1-pyrrolidinyl)propionate, ethyl 3-morpholinopropionate, methoxycarbonylmethyl 3-piperidinopropionate, 2-hydroxyethyl 3-(1-pyrrolidinyl)propionate, 2-acetoxyethyl 3-morpholinopropionate, 2-oxotetrahydrofuran-3-yl 3-(1-pyrrolidinyl)propionate, tetrahydrofurfuryl 3-morpholinopropionate, glycidyl 3-piperidinopropionate, 2-methoxyethyl 3-morpholinopropionate, 2-(2-methoxyethoxy)ethyl 3-(1-pyrrolidinyl)propionate, butyl 3-morpholinopropionate, cyclohexyl 3-piperidinopropionate, β-(1-pyrrolidinyl)methyl-γ-butyrolactone, β-piperidino-γ-butyrolactone, β-morpholino-δ-valerolactone, methyl 1-pyrrolidinylacetate, methyl piperidinoacetate, methyl morpholinoacetate, methyl thiomorpholinoacetate, ethyl 1-pyrrolidinylacetate, and 2-methoxyethyl morpholinoacetate.

Also, one or more of cyano-bearing basic compounds having the following general formulae (D3) to (D6) may be blended.

Herein, X′, R³⁰⁷ and w are as defined above, and R³⁰⁸ and R³⁰⁹ each are independently a straight or branched alkylene group of 1 to 4 carbon atoms.

Illustrative examples of the cyano-bearing basic compounds having formulae (D3) to (D6) include 3-(diethylamino)propiononitrile, N,N-bis(2-hydroxyethyl)-3-aminopropiononitrile, N,N-bis(2-acetoxyethyl)-3-aminopropiononitrile, N,N-bis(2-formyloxyethyl)-3-aminopropiononitrile, N,N-bis(2-methoxyethyl)-3-aminopropiononitrile, N,N-bis[2-(methoxymethoxy)ethyl]-3-aminopropiononitrile, methyl N-(2-cyanoethyl)-N-(2-methoxyethyl)-3-aminopropionate, methyl N-(2-cyanoethyl)-N-(2-hydroxyethyl)-3-aminopropionate, methyl N-(2-acetoxyethyl)-N-(2-cyanoethyl)-3-aminopropionate, N-(2-cyanoethyl)-N-ethyl-3-aminopropiononitrile, . N-(2-cyanoethyl)-N-(2-hydroxyethyl)-3-aminopropiononitrile, N-(2-acetoxyethyl)-N-(2-cyanoethyl)-3-aminopropiononitrile, N-(2-cyanoethyl)-N-(2-formyloxyethyl)-3-aminopropiononitrile, N-(2-cyanoethyl)-N-(2-methoxyethyl)-3-aminopropiononitrile, N-(2-cyanoethyl)-N-[2-(methoxymethoxy)ethyl]-3-aminopropiononitrile, N-(2-cyanoethyl)-N-(3-hydroxy-1-propyl)-3-aminopropiononitrile, N-(3-acetoxy-1-propyl)-N-(2-cyanoethyl)-3-aminopropiononitrile, N-(2-cyanoethyl)-N-(3-formyloxy-1-propyl)-3-aminopropiononitrile, N-(2-cyanoethyl)-N-tetrahydrofurfuryl-3-aminopropiononitrile, N,N-bis(2-cyanoethyl)-3-aminopropiononitrile, diethylaminoacetonitrile, N,N-bis(2-hydroxyethyl)aminoacetonitrile, N,N-bis(2-acetoxyethyl)aminoacetonitrile, N,N-bis(2-formyloxyethyl)aminoacetonitrile, N,N-bis(2-methoxyethyl)aminoacetonitrile, N,N-bis[2-(methoxymethoxy)ethyl]aminoacetonitrile, methyl N-cyanomethyl-N-(2-methoxyethyl)-3-aminopropionate, methyl N-cyanomethyl-N-(2-hydroxyethyl)-3-aminopropionate, methyl N-(2-acetoxyethyl)-N-cyanomethyl-3-aminopropionate, N-cyanomethyl-N-(2-hydroxyethyl)aminoacetonitrile, N-(2-acetoxyethyl)-N-(cyanomethyl)aminoacetonitrile, N-cyanomethyl-N-(2-formyloxyethyl)aminoacetonitrile, N-cyanomethyl-N-(2-methoxyethyl)aminoacetonitrile, N-cyanomethyl-N-[2-(methoxymethoxy)ethyl)aminoacetonitrile, N-cyanomethyl-N-(3-hydroxy-1-propyl)aminoacetonitrile, N-(3-acetoxy-1-propyl)-N-(cyanomethyl)aminoacetonitrile, N-cyanomethyl-N-(3-formyloxy-1-propyl)aminoacetonitrile, N,N-bis(cyanomethyl)aminoacetonitrile, 1-pyrrolidinepropiononitrile, 1-piperidinepropiononitrile, 4-morpholinepropiononitrile, 1-pyrrolidineacetonitrile, 1-piperidineacetonitrile, 4-morpholineacetonitrile, cyanomethyl 3-diethylaminopropionate, cyanomethyl N,N-bis(2-hydroxyethyl)-3-aminopropionate, cyanomethyl N,N-bis(2-acetoxyethyl)-3-aminopropionate, cyanomethyl N,N-bis(2-formyloxyethyl)-3-aminopropionate, cyanomethyl N,N-bis(2-methoxyethyl)-3-aminopropionate, cyanomethyl N,N-bis[2-(methoxymethoxy)ethyl]-3-aminopropionate, 2-cyanoethyl 3-diethylaminopropionate, 2-cyanoethyl N,N-bis(2-hydroxyethyl)-3-aminopropionate, 2-cyanoethyl N,N-bis(2-acetoxyethyl)-3-aminopropionate, 2-cyanoethyl N,N-bis(2-formyloxyethyl)-3-aminopropionate, 2-cyanoethyl N,N-bis(2-methoxyethyl)-3-aminopropionate, 2-cyanoethyl N,N-bis[2-(methoxymethoxy)ethyl]-3-aminopropionate, cyanomethyl 1-pyrrolidinepropionate, cyanomethyl 1-piperidinepropionate, cyanomethyl 4-morpholinepropionate, 2-cyanoethyl 1-pyrrolidinepropionate, 2-cyanoethyl 1-piperidinepropionate, and 2-cyanoethyl 4-morpholinepropionate.

The basic compounds may be used alone or in admixture of two or more. The basic compound is preferably formulated in an amount of 0 to 2 parts, and especially 0.01 to 1 part by weight, among 100 parts by weight of the solids in the resist composition. The use of more than 2 parts of the basis compound would result in too low a sensitivity.

Component (E)

Illustrative, non-limiting, examples of the organic acid derivatives (E) include phenol, cresol, catechol, resorcinol, pyrogallol, phloroglucin, bis(4-hydroxyphenyl)methane, 2,2-bis(4′-hydroxyphenyl)propane, bis(4-hydroxyphenyl)sulfone, 1,1,1-tris(4′-hydroxyphenyl)ethane, 1,1,2-tris(4′-hydroxyphenyl)ethane, hydroxybenzophenone, 4-hydroxyphenylacetic acid, 3-hydroxyphenylacetic acid, 2-hydroxyphenylacetic acid, 3-(4-hydroxyphenyl)propionic acid, 3-(2-hydroxyphenyl)propionic acid, 2,5-dihydroxyphenylacetic acid, 3,4-dihydroxyphenylacetic acid, 1,2-phenylenediacetic acid, 1,3-phenylenediacetic acid, 1,4-phenylenediacetic acid, 1,2-phenylenedioxydiacetic acid, 1,4-phenylenedipropanoic acid, benzoic acid, salicylic acid, 4,4-bis(4′-hydroxyphenyl)valeric acid, 4-tert-butoxyphenylacetic acid, 4-(4-hydroxyphenyl)butyric acid, 3,4-dihydroxymandelic acid, and 4-hydroxymandelic acid. Of these, salicylic acid and 4,4-bis(4′-hydroxyphenyl)valeric acid are preferred. They may be used alone or in admixture of two or more.

In the resist composition of the invention, the organic acid derivative is preferably formulated in an amount of up to 5 parts, and especially up to 1 part by weight, among 100 parts by weight of the solids in the resist composition. The use of more than 5 parts of the organic acid derivative would result in too low a resolution. Depending on the combination of the other components in the resist composition, the organic acid derivative may be omitted.

Component (F)

Component (F) is an organic solvent. Illustrative, non-limiting, examples include butyl acetate, amyl acetate, cyclohexyl acetate, 3-methoxybutyl acetate, methyl ethyl ketone, methyl amyl ketone, cyclohexanone, cyclopentanone, 3-ethoxyethyl propionate, 3-ethoxymethyl propionate, 3-methoxymethyl propionate, methyl acetoacetate, ethyl acetoacetate, diacetone alcohol, methyl pyruvate, ethyl pyruvate, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monomethyl ether propionate, propylene glycol monoethyl ether propionate, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, 3-methyl-3-methoxybutanol, N-methylpyrrolidone, dimethyl sulfoxide, γ-butyrolactone; propylene glycol alkyl ether acetates such as propylene glycol methyl ether acetate, propylene glycol ethyl ether acetate, propylene glycol propyl ether acetate; alkyl lactates such as methyl lactate, ethyl lactate, propyl lactate; and tetramethylene sulfone. Of these, the propylene glycol alkyl ether acetates and alkyl lactates are especially preferred. The solvents may be used alone or in admixture of two or more. An exemplary useful solvent mixture is a mixture of a propylene glycol alkyl ether acetate and an alkyl lactate. It is noted that the alkyl groups of the propylene glycol alkyl ether acetates are preferably those of 1 to 4 carbon atoms, for example, methyl, ethyl and propyl, with methyl and ethyl being especially preferred. Since the propylene glycol alkyl ether acetates include 1,2- and 1,3-substituted ones, each includes three isomers depending on the combination of substituted positions, which may be used alone or in admixture. It is also noted that the alkyl groups of the alkyl lactates are preferably those of 1 to 4 carbon atoms, for example, methyl, ethyl and propyl, with methyl and ethyl being especially preferred.

When the propylene glycol alkyl ether acetate is used as the solvent, it preferably accounts for at least 50% by weight of the entire solvent. Also when the alkyl lactate is used as the solvent, it preferably accounts for at least 50% by weight of the entire solvent. When a mixture of propylene glycol alkyl ether acetate and alkyl lactate is used as the solvent, that mixture preferably accounts for at least 50% by weight of the entire solvent.

The solvent is preferably used in an amount of 300 to 2,000 parts by weight, especially 400 to 1,000 parts by weight, relative to 100 parts by weight of the solids in the resist composition. The solvent concentration is not limited thereto as long as a film can be formed by existing methods.

Component (G)

In one preferred embodiment, the resist composition further contains (G) a compound with a molecular weight of up to 3,000 which changes its solubility in an alkaline developer under the action of an acid, that is, a dissolution inhibitor. Typically, a compound obtained by partially or entirely substituting acid labile substituents on a phenol or carboxylic acid derivative having a molecular weight of up to 3,000, especially up to 2,500 is added as the dissolution inhibitor.

Examples of the phenol or carboxylic acid derivative having a molecular weight of up to 2,500 include bisphenol A, bisphenol H, bisphenol S, 4,4-bis(4′-hydroxyphenyl)valeric acid, tris(4-hydroxyphenyl)methane, 1,1,1-tris(4′-hydroxyphenyl)ethane, 1,1,2-tris(4′-hydroxyphenyl)ethane, phenolphthalein, and thymolphthalein. The acid labile substituents are the same as those exemplified as the acid labile groups in the polymer.

Illustrative, non-limiting, examples of the dissolution inhibitors which are useful herein include bis(4-(2′-tetrahydropyranyloxy)phenyl)methane, bis(4-(2′-tetrahydrofuranyloxy)phenyl)methane, bis(4-tert-butoxyphenyl)methane, bis(4-tert-butoxycarbonyloxyphenyl)methane, bis(4-tert-butoxycarbonylmethyloxyphenyl)methane, bis(4-(1′-ethoxyethoxy)phenyl)methane, bis(4-(1′-ethoxypropyloxy)phenyl)methane, 2,2-bis(4′-(2″-tetrahydropyranyloxy))propane, 2,2-bis(4′-(2″-tetrahydrofuranyloxy)phenyl)propane, 2,2-bis(4′-tert-butoxyphenyl)propane, 2,2-bis(4′-tert-butoxycarbonyloxyphenyl)propane, 2,2-bis(4-tert-butoxycarbonylmethyloxyphenyl)propane, 2,2-bis(4′-(1″-ethoxyethoxy)phenyl)propane, 2,2-bis(4′-(1″-ethoxypropyloxy)phenyl)propane, tert-butyl 4,4-bis(4′-(2″-tetrahydropyranyloxy)phenyl)valerate, tert-butyl 4,4-bis(4′-(2″-tetrahydrofuranyloxy)phenyl)valerate, tert-butyl 4,4-bis(4′-tert-butoxyphenyl)valerate, tert-butyl 4,4-bis(4-tert-butoxycarbonyloxyphenyl)valerate, tert-butyl 4,4-bis(4′-tert-butoxycarbonylmethyloxyphenyl)valerate, tert-butyl 4,4-bis(4′-(1″-ethoxyethoxy)phenyl)valerate, tert-butyl 4,4-bis(4′-(1″-ethoxypropyloxy)phenyl)valerate, tris(4-(2′-tetrahydropyranyloxy)phenyl)methane, tris(4-(2′-tetrahydrofuranyloxy)phenyl)methane, tris(4-tert-butoxyphenyl)methane, tris(4-tert-butoxycarbonyloxyphenyl)methane, tris(4-tert-butoxycarbonyloxymethylphenyl)methane, tris(4-(1′-ethoxyethoxy)phenyl)methane, tris(4-(1′-ethoxypropyloxy)phenyl)methane, 1,1,2-tris(4′-(2″-tetrahydropyranyloxy)phenyl)ethane, 1,1,2-tris(4′-(2″-tetrahydrofuranyloxy)phenyl)ethane, 1,1,2-tris(4′-tert-butoxyphenyl)ethane, 1,1,2-tris(4′-tert-butoxycarbonyloxyphenyl)ethane, 1,1,2-tris(4′-tert-butoxycarbonylmethyloxyphenyl)ethane, 1,1,2-tris(4′-(1′-ethoxyethoxy)phenyl)ethane, and 1,1,2-tris(4′-(1′-ethoxypropyloxy)phenyl)ethane.

In the resist composition of the invention, an appropriate amount of the dissolution inhibitor is up to 20 parts, and especially up to 15 parts by weight, among 100 parts by weight of the solids in the resist composition. With more than 20 parts of the dissolution inhibitor, the resist composition becomes less heat resistant because of an increased content of monomer components.

Component (H)

In a chemically amplified negative resist composition as well, the O-arenesulfonyloxime compound of formula (1) or (1a) according to the invention may be used as the photoacid generator. This composition further contains an alkali-soluble resin as component (H), examples of which are intermediates of the above-described component (A), though not limited thereto. Examples of the alkali-soluble resin include poly(p-hydroxystyrene), poly(m-hydroxystyrene), poly(4-hydroxy-2-methylstyrene), poly(4-hydroxy-3-methylstyrene), poly(α-methyl-p-hydroxystyrene), partially hydrogenated p-hydroxystyrene copolymers, p-hydroxystyrene-α-methyl-p-hydroxystyrene copolymers, p-hydroxystyrene-α-methylstyrene copolymers, p-hydroxystyrene-styrene copolymers, p-hydroxystyrene-m-hydroxystyrene copolymers, p-hydroxystyrene-styrene copolymers, p-hydroxystyrene-acrylic acid copolymers, p-hydroxystyrene-methacrylic acid copolymers, p-hydroxystyrene-methyl methacrylate copolymers, p-hydroxystyrene-acrylic acid-methyl methacrylate copolymers, p-hydroxystyrene-methyl acrylate copolymers, p-hydroxystyrene-methacrylic acid-methyl methacrylate copolymers, poly(methacrylic acid), poly(acrylic acid), acrylic acid-methyl acrylate copolymers, methacrylic acid-methyl methacrylate copolymers, acrylic acid-maleimide copolymers, methacrylic acid-maleimide copolymers, p-hydroxystyrene-acrylic acid-maleimide copolymers, and p-hydroxystyrene-methacrylic acid-maleimide copolymers, but are not limited to these combinations.

Preferred are poly(p-hydroxystyrene), partially hydrogenated p-hydroxystyrene copolymers, p-hydroxystyrene-styrene copolymers, p-hydroxystyrene-acrylic acid copolymers, and p-hydroxystyrene-methacrylic acid copolymers.

Alkali-soluble resins comprising recurring units of the following formula (2), (2′), (2″) or (2′″) are especially preferred.

Herein R¹ is hydrogen or methyl; and R² is a straight, branched or cyclic alkyl group of 1 to 8 carbon atoms. The subscript x is 0 or a positive integer; y is a positive integer, satisfying x+y≦5, z is 0 or a positive integer, satisfying x+z≦5; M and N are positive integers, satisfying 0<M/(M+N)≦0.5; yy is 0 or a positive integer, satisfying x+yy≦4; A and B are positive integers, C is 0 or a positive integer, satisfying 0<B/(A+B+C)≦0.5, ZZ is a divalent organic group selected from among CH₂, CH(OH), CR²(OH), C═O and C(OR²)(OH), or a trivalent organic group represented by —C(OH)═; F is independently a positive integer, and H is a positive integer, satisfying 0.001≦H/(F+H)≦0.1; and XX is 1 or 2.

The alkali-soluble resin or polymer should preferably have a weight average molecular weight (Mw) of 3,000 to 100,000. Many polymers with Mw of less than 3,000 do not perform well and are poor in heat resistance and film formation. Many polymers with Mw of more than 100,000 give rise to a problem with respect to dissolution in the resist solvent and developer. The polymer should also preferably have a dispersity (Mw/Mn) of up to 3.5, and more preferably up to 1.5. With a dispersity of more than 3.5, resolution is low in many cases. Although the preparation method is not critical, a poly(p-hydroxystyrene) or similar polymer with a low dispersity or narrow dispersion can be synthesized by living anion polymerization.

To impart a certain function, suitable substituent groups may be introduced into some of the phenolic hydroxyl and carboxyl groups on the foregoing polymer with protected acid labile groups. Exemplary and preferred are substituent groups for improving adhesion to the substrate, substituent groups for improving etching resistance, and especially substituent groups which are relatively stable against acid and alkali and effective for controlling such that the dissolution rate in an alkali developer of unexposed and low exposed areas of a resist film may not become too high.

Illustrative, non-limiting, substituent groups include 2-hydroxyethyl, 2-hydroxypropyl, methoxymethyl, methoxycarbonyl, ethoxycarbonyl, methoxycarbonylmethyl, ethoxycarbonylmethyl, 4-methyl-2-oxo-4-oxolanyl, 4-methyl-2-oxo-4-oxanyl, methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, acetyl, pivaloyl, adamantyl, isoboronyl, and cyclohexyl. It is also possible to introduce acid-decomposable substituent groups such as t-butoxycarbonyl and relatively acid-undecomposable substituent groups such as t-butyl and t-butoxycarbonylmethyl.

In the resist composition, the above resin (H) is blended in any desired amount, preferably of 65 to 99 parts by weight, especially 65 to 98 parts by weight among 100 parts by weight of the solids.

Component (I)

Also contained in the negative resist composition is (I) an acid crosslinker capable of forming a crosslinked structure under the action of an acid. Typical acid crosslinkers are compounds having at least two hydroxymethyl, alkoxymethyl, epoxy or vinyl ether groups in a molecule. Substituted glycoluril derivatives, urea derivatives, and hexa(methoxymethyl)melamine compounds are suitable as the acid crosslinker in the chemically amplified, negative resist composition. Examples include N,N,N′,N′-tetramethoxymethylurea, hexamethoxymethylmelamine, tetraalkoxymethyl-substituted glycoluril compounds such as tetrahydroxymethyl-substituted glycoluril and tetramethoxymethylglycoluril, and condensates of phenolic compounds such as substituted or unsubstituted bis(hydroxymethylphenol) compounds and bisphenol A with epichlorohydrin. Especially preferred acid crosslinkers include 1,3,5,7-tetraalkoxymethylglycolurils such as 1,3,5,7-tetramethoxymethylglycoluril, as well as 1,3,5,7-tetrahydroxymethylglycoluril, 2,6-dihydroxymethyl-p-cresol, 2,6-dihydroxymethylphenol, 2,2′,6,6′-tetrahydroxymethyl-bisphenol A, 1,4-bis[2-(2-hydroxypropyl)]benzene, N,N,N′,N′-tetramethoxymethylurea, and hexamethoxymethylmelamine.

An appropriate amount of the acid crosslinker is, but not limited thereto, about 1 to 20 parts, and especially about 5 to 15 parts by weight among 100 parts by weight of the solids in the resist composition. The acid crosslinkers may be used alone or in admixture of any.

Component (J)

Component (J) is an alkali-soluble compound having a molecular weight of up to 2,500. Any suitable compound may be used although a compound having at least two phenol and/or carboxyl groups is preferred. Illustrative, non-limiting, examples of the alkali-soluble compound (J) include cresol, catechol, resorcinol, pyrogallol, phloroglucin, bis(4-hydroxyphenyl)methane, 2,2-bis(4′-hydroxyphenyl)propane, bis(4-hydroxyphenyl)sulfone, 1,1,1-tris(4′-hydroxyphenyl)ethane, 1,1,2-tris(4′-hydroxyphenyl)ethane, hydroxybenzophenone, 4-hydroxyphenylacetic acid, 3-hydroxyphenylacetic acid, 2-hydroxyphenylacetic acid, 3-(4-hydroxyphenyl)propionic acid, 3-(2-hydroxyphenyl)propionic acid, 2,5-dihydroxyphenylacetic acid, 3,4-dihydroxyphenylacetic acid, 1,2-phenylenediacetic acid, 1,3-phenylenediacetic acid, 1,4-phenylenediacetic acid, 1,2-phenylenedioxydiacetic acid, 1,4-phenylenedipropanoic acid, benzoic acid, salicylic acid, 4,4-bis(4′-hydroxyphenyl)valeric acid, 4-tert-butoxyphenylacetic acid, 4-(4-hydroxyphenyl)butyric acid, 3,4-dihydroxymandelic acid, and 4-hydroxymandelic acid. Of these, salicylic acid and 4,4-bis(4′-hydroxyphenyl)valeric acid are preferred. They may be used alone or in admixture of two or more. The alkali-soluble compound is blended in any desired amount, preferably of 0 to 20 parts by weight, especially 2 to 10 parts by weight among 100 parts by weight of the solids in the resist composition.

In the chemically amplified resist composition of the invention, there may be added such additives as surfactants for improving coating, light absorbing agents (typically, UV absorbers) for reducing diffuse reflection from the substrate, and thermal flow regulators.

Illustrative, non-limiting, examples of the surfactant include nonionic surfactants, for example, polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene cetyl ether, and polyoxyethylene oleyl ether, polyoxyethylene alkylaryl ethers such as polyoxyethylene octylphenol ether and polyoxyethylene nonylphenol ether, polyoxyethylene polyoxypropylene block copolymers, sorbitan fatty acid esters such as sorbitan monolaurate, sorbitan monopalmitate, and sorbitan monostearate, and polyoxyethylene sorbitan fatty acid esters such as polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan trioleate, and polyoxyethylene sorbitan tristearate; fluorochemical surfactants such as EFTOP EF301, EF303 and EF352 (Tohkem Products Co., Ltd.), Megaface F171, F172 and F173 (Dai-Nippon Ink & Chemicals, Inc.), Fluorad FC430 and FC431 (Sumitomo 3M Co., Ltd.), Aashiguard AG710, Surflon S-381, S-382, SC101, SC102, SC103, SC104, SC105, SC106, Surfynol E1004, KH-10, KH-20, KH-30 and KH-40 (Asahi Glass Co., Ltd.); organosiloxane polymers KP341, X-70-092 and X-70-093 (Shin-Etsu Chemical Co., Ltd.), acrylic acid or methacrylic acid Polyflow No. 75 and No. 95 (Kyoeisha Ushi Kagaku Kogyo Co., Ltd.). Inter alia, FC430, Surflon S-381, Surfynol E1004, KH-20 and KH-30 are preferred. These surfactants may be used alone or in admixture.

In the chemically amplified resist composition according to the invention, the surfactant is preferably formulated in an amount of up to 2 parts, and especially up to 1 part by weight, among 100 parts by weight of the solids in the resist composition.

In the chemically amplified resist composition according to the invention, UV absorbers may be added. Those UV absorbers described in JP-A 11-190904 are useful, but the invention is not limited thereto. Exemplary UV absorbers are diaryl sulfoxide derivatives such as bis(4-hydroxyphenyl) sulfoxide, bis(4-tert-butoxyphenyl) sulfoxide, bis(4-tert-butoxycarbonyloxyphenyl) sulfoxide, and bis[4-(1-ethoxyethoxy)phenyl]sulfoxide; diarylsulfone derivatives such as bis(4-hydroxyphenyl)sulfone, bis(4-tert-butoxyphenyl)sulfone, bis(4-tert-butoxycarbonyloxyphenyl)sulfone, bis[4-(1-ethoxyethoxy)phenyl]sulfone, and bis[4-(1-ethoxypropoxy)phenyl]sulfone; diazo compounds such as benzoquinonediazide, naphthoquinonediazide, anthraquinonediazide, diazofluorene, diazotetralone, and diazophenanthrone; quinonediazide group-containing compounds such as complete or partial ester compounds between naphthoquinone-1,2-diazide-5-sulfonic acid chloride and 2,3,4-trihydroxybenzophenone and complete or partial ester compounds between naphthoquinone-1,2-diazide-4-sulfonic acid chloride and 2,4,4′-trihydroxybenzophenone; tert-butyl 9-anthracenecarboxylate, tert-amyl 9-anthracenecarboxylate, tert-methoxymethyl 9-anthracenecarboxylate, tert-ethoxyethyl 9-anthracenecarboxylate, 2-tert-tetrahydropyranyl 9-anthracenecarboxylate, and 2-tert-tetrahydrofuranyl 9-anthracenecarboxylate. The UV absorber may or may not be added to the resist composition depending on the type of resist composition. An appropriate amount of UV absorber, if added, is 0 to 10 parts, more preferably 0.5 to 10 parts, most preferably 1 to 5 parts by weight, among 100 parts by weight of the base resin.

Suitable thermal flow regulators are organic compounds which do not react with any components in the resist composition or alter the resolution capability thereof, and preferably aliphatic compounds having pH 5.0 to 8.0 and a boiling point of at least 200° C. under atmospheric pressure. Preferred examples include, but are not limited to, polyoxyalkylene alkyl ether esters, polyoxyalkylene alkyl ethers, polyoxyalkylene dialkyl ethers, polyoxyalkylene aralkyl alkyl ethers, polyoxyalkylene aralkyl ethers, polyoxyalkylene diaralkyl ethers, and polyoxyalkylene laurates. Also useful are polyoxyethylene nonyl phenyl ether, polyoxyethylene alkyl ethers, polyoxyethylene lauryl ether, polyoxyethylene higher alcohol ethers, polyoxyalkylene alkyl ethers, polyoxyethylene derivatives, and polyoxyethylene sorbitan monolaurate. These compounds may be used alone or in admixture of two or more. Commercially available thermal flow regulators include Sunmol N-60SM (polyoxyethylene nonyl phenyl ether), L-50 (polyoxyethylene alkyl ether), and SE-70 (polyoxyethylene alkyl ether), available from Nicca Chemical Co., Ltd.; and Emulgen 108 (polyoxyethylene lauryl ether), 707 (polyoxyethylene higher alcohol ether), 709 (polyoxyethylene higher alcohol ether), LS-106 (polyoxyalkylene alkyl ether), LS-110 (polyoxyalkylene alkyl ether), MS-110 (polyoxyalkylene alkyl ether), A-60 (polyoxyethylene derivative), B-66 (polyoxyethylene derivative), and Rheodol TW-L106 (polyoxyethylene sorbitan monolaurate), all available from Kao Corp. Inter alia, Emulgen MS-110 and Rheodol TW-L106 are preferred.

An appropriate flow quantity may be achieved by regulating the amount of the above organic compound added to the resist composition, preferably in a range of 0.2 to 5% by weight, more preferably 0.5 to 2% by weight based on the weight of the base resin. For more detail, reference should be made to JP-A 2004-333779.

For the microfabrication of integrated circuits, any well-known lithography may be used to form a resist pattern from the chemically amplified resist composition comprising the photoacid generator of formula (1) or (1a) according to the invention.

The composition is applied onto a substrate (e.g., Si, SiO₂, SiN, SiON, TiN, WSi, BPSG, SOG, organic anti-reflecting film, etc.) for microfabrication by a suitable coating technique such as spin coating, roll coating, flow coating, dip coating, spray coating or doctor coating. The coating is prebaked on a hot plate at a temperature of 60 to 150° C. for about 1 to 10 minutes, preferably 80 to 120° C. for 1 to 5 minutes. The resulting resist film is generally 0.1 to 2.0 μm thick. Through a photomask having a desired pattern, the resist film is then exposed to radiation, preferably having an exposure wavelength of up to 300 nm, such as UV, deep-UV, electron beams, x-rays, excimer laser light, γ-rays and synchrotron radiation. The preferred light source is a beam from an excimer laser, especially KrF excimer laser or deep UV of 245-255 nm wavelength. The exposure dose is preferably in the range of about 1 to 200 mJ/cm², more preferably about 10 to 100 mJ/cm². The film is post-exposure baked (PEB) on a hot plate at 60 to 150° C. for 1 to 5 minutes, preferably 80 to 120° C. for 1 to 3 minutes.

Thereafter the resist film is developed with a developer in the form of an aqueous base solution, for example, 0.1 to 5%, preferably 2 to 3% aqueous solution of tetramethylammonium hydroxide (TMAH) for 0.1 to 3 minutes, preferably 0.5 to 2 minutes by conventional techniques such as dip, puddle or spray development. In this way, a desired resist pattern is formed on the substrate. It is appreciated that the resist composition of the invention is best suited for micro-patterning using such actinic radiation as deep UV with a wavelength of 254 to 193 nm, vacuum UV with a wavelength of 157 nm, electron beams, x-rays, excimer laser light, γ-rays and synchrotron radiation. With any of the above-described parameters outside the above-described range, the process may sometimes fail to produce the desired pattern.

Where a thermal flow step is involved, a resist pattern, especially a contact hole pattern which has been formed as mentioned above is heated on a hot plate. The heating temperature for thermal flow is preferably in a range of 100 to 200° C., and more preferably 100 to 150° C. with the precision of the hot plate being taken into account. The heat treatment time is preferably 60 to 120 seconds. While the contact hole pattern formed by exposure and development generally has a size of 0.20 to 0.30 μm, the thermal flow reduces the contact hole size, enabling formation of a ultrafine contact hole pattern with a size of 0.10 to 0.15 μM.

EXAMPLE

Examples of the invention are given below by way of illustration and not by way of limitation. Mw is weight average molecular weight.

Synthesis Example 1 Synthesis of sodium 4-(4′-methylphenylsulfonyloxy)benzenesulfonate

In 400 g of tetrahydrofuran and 250 g of water were dissolved 208 g (1.0 mol) of 4-phenolsulfonic acid hydrate and 191 g (1.0 mol) of p-toluenesulfonic acid chloride. With ice cooling and stirring, an aqueous sodium hydroxide solution (80 g (2.0 mol) of sodium hydroxide in 125 g of water) was added dropwise such that the temperature might not exceed 20° C. After the completion of dropwise addition, the solution was allowed to ripen for 2 hours at room temperature. To the reaction solution, 700 g of dichloromethane was added to help sodium 4-(4′-methylphenylsulfonyloxy)benzenesulfonate crystallize. The crystals were collected by filtration, washed with 200 g of dichloromethane, and dried in vacuum at 60° C. for 12 hours. The amount was 330 g (yield 94%).

Synthesis Example 2 Synthesis of sodium 2,5-bis(4′-methylphenylsulfonyloxy)benzenesulfonate

By substantially following Synthesis Example 1 except that 1.0 mol of potassium hydroquinonesulfonate was used instead of the 4-phenolsulfonic acid hydrate and 2.5 mol of p-toluenesulfonic acid chloride was used, the target compound, sodium 2,5-bis(4′-methylphenylsulfonyloxy)benzenesulfonate was synthesized.

Synthesis Example 3 Synthesis of sodium 6-(4′-methylphenylsulfonyloxy)naphthalene-2-sulfonate

In 100 g of tetrahydrofuran and 80 g of water were dissolved 50 g (0.18 mol) of sodium 2,6-naphtholsulfonate hydrate and 33.8 g (0.18 mol) of p-toluenesulfonic acid chloride. With ice cooling and stirring, an aqueous sodium hydroxide solution (7.1 g (0.18 mol) of sodium hydroxide in 30 g of water) was added dropwise such that the temperature might not exceed 20° C. After the completion of dropwise addition, the solution was allowed to ripen for 2 hours at room temperature. To the reaction solution, 600 g of dichloromethane was added to help sodium 6-(4′-methylphenylsulfonyloxy)naphthalene-2-sulfonate crystallize. The crystals were collected by filtration, washed with 300 g of dichloromethane, and dried in vacuum at 60° C. for 12 hours. The amount was 62 g (yield 86%).

Synthesis Example 4 Synthesis of sodium 4-(4′-methylphenylsulfonyloxy)naphthalene-1-sulfonate

In 59 g of tetrahydrofuran and 23 g of water were dissolved 25 g (0.09 mol) of sodium 1,4-naphtholsulfonate hydrate and 16.8 g (0.09 mol) of p-toluenesulfonic acid chloride. With ice cooling and stirring, an aqueous sodium hydroxide solution (3.5 g (0.09 mol) of sodium hydroxide in 27 g of water) was added dropwise such that the temperature might not exceed 20° C. After the completion of dropwise addition, the solution was allowed to ripen for 2 hours at room temperature. To the reaction solution, 700 g of dichloromethane was added to help sodium 4-(4′-methylphenylsulfonyloxy)naphthalene-1-sulfonate crystallize. The crystals were collected by filtration, washed with 300 g of dichloromethane, and dried in vacuum at 60° C. for 12 hours. The amount was 30 g (yield 83%).

Synthesis Example 5 Synthesis of sodium 8-(4′-methylphenylsulfonyloxy)naphthalene-1-sulfonate

In 24 g of tetrahydrofuran and 11 g of water were dissolved 12.3 g (0.05 mol) of sodium 1,8-naphtholsulfonate hydrate and 9.5 g (0.05 mol) of p-toluenesulfonic acid chloride. With ice cooling and stirring, an aqueous sodium hydroxide solution (2 g (0.05 mol) of sodium hydroxide in 9 g of water) was added dropwise such that the temperature might not exceed 20° C. After the completion of dropwise addition, the solution was allowed to ripen for 2 hours at room temperature. To the reaction solution, 100 g of dichloromethane was added to help sodium 8-(4′-methylphenylsulfonyloxy)naphthalene-1-sulfonate crystallize. The crystals were collected by filtration, washed with 300 g of dichloromethane, and dried in vacuum at 60° C. for 12 hours. The amount was 17 g (yield 85%).

Synthesis Example 6 Synthesis of sodium 3-methoxy-4-(4′-methylphenylsulfonyloxy)benzenesulfonate

In 80 g of tetrahydrofuran and 65 g of water were dissolved 50 g (0.2 mol) of potassium guaiacolsulfonate hydrate and 38 g (0.2 mol) of p-toluenesulfonic acid chloride. With ice cooling and stirring, an aqueous sodium hydroxide solution (8 g (0.2 mol) of sodium hydroxide in 15 g of water) was added dropwise such that the temperature might not exceed 20° C. After the completion of dropwise addition, the solution was allowed to ripen for 2 hours at room temperature. To the reaction solution, 200 g of dichloromethane was added to help sodium 3-methoxy-4-(4′-methylphenylsulfonyloxy)benzenesulfonate crystallize. The crystals were collected by filtration, washed with 200 g of dichloromethane, and dried in vacuum at 60° C. for 12 hours. The amount was 72 g (yield 94% as Na salt).

It is noted that the crystalline product thus obtained could be a mixture of sodium and potassium salts. The product was directly used in the subsequent step of halogenation reaction without purification because the metals can be removed as sodium and potassium ions in the halogenation reaction.

Synthesis Example 7 Synthesis of 4-(4′-methylphenylsulfonyloxy)benzenesulfonyl chloride

In 80 g of carbon tetrachloride, 20 g (0.057 mol) of sodium 4-(4′-methylphenylsulfonyloxy)benzenesulfonate, obtained in Synthesis Example 1, was dispersed by stirring under ice cooling. To the suspension, 23.8 g (0.114 mol) of phosphorus pentachloride was slowly added such that the temperature might not exceed 20° C. The suspension was stirred for one hour under ice cooling and then for 12 hours at room temperature. After the ripening, the reaction solution was poured into 150 g of ice water whereupon a white oily matter separated out. The oily matter was extracted with 100 g of dichloromethane, dried over anhydrous magnesium sulfate, and filtered. The solvent was distilled off in vacuum, yielding 15.9 g of white crystals (yield 81%).

Synthesis Examples 8-12

The procedure of Synthesis Example 7 was repeated aside from using the arylsulfonyloxyarylsulfonic acid salts of Synthesis Examples 2 to 6 instead of the sodium 4-(4′-methylphenylsulfonyloxy)benzenesulfonate used in Synthesis Example 7. The corresponding sulfonyl chlorides were accordingly synthesized.

Synthesis Example 8 2,5-bis(4′-methylphenylsulfonyloxy)benzenesulfonyl chloride Synthesis Example 9 6-(4′-methylphenylsulfonyloxy)naphthalene-2-sulfonyl chloride Synthesis Example 10 4-(4′-methylphenylsulfonyloxy)naphthalene-1-sulfonyl chloride Synthesis Example 11 8-(4′-methylphenylsulfonyloxy)naphthalene-1-sulfonyl chloride Synthesis Example 12 3-methoxy-4-(4′-methylphenylsulfonyloxy)benzenesulfonyl chloride Synthesis Example 13

Synthesis was carried out as in Synthesis Example 7 aside from using O-cresolsulfonic acid instead of the 4-phenolsulfonic acid hydrate in Synthesis Example 1, yielding 3-methyl-4-(4′-methylphenylsulfonyloxy)benzenesulfonyl chloride.

Synthesis Example 14 Synthesis of (3-(hydroxy)imino-3H-thiophen-2-ylidene)-(2-methylphenyl)-acetonitrile

A solution of 128 g (2.3 mol) of potassium hydroxide in 364 g of methanol was cooled, to which 75 g (0.57 mol) of o-xylyl cyamide was added. Thereafter, a solution of 75 g (0.58 mol) of 2-nitrothiophene (purity 85%) in 218 g of methanol was added dropwise such that the temperature might not exceed 5° C. The solution was allowed to ripen for 30 minutes below 5° C., after which a solution of 551 g of glacial acetic acid in 2,200 g of water was added, and further 1,000 g of ethyl acetate added. The organic layer was separated. Ethyl acetate, 400 g, was added to the aqueous layer to effect extraction again. The organic layers were combined, washed with 200 g of saturated sodium chloride water two times, dried over anhydrous magnesium sulfate, and concentrated in vacuum, obtaining 125 g of an oily matter. It was purified by silica gel column chromatography (eluent, ethyl acetate:hexane=2:1 by volume). The elute was concentrated, followed by recrystallization from toluene, filtration and drying. There was obtained 49 g of yellow crystals (yield 35%).

The compound was analyzed by nuclear magnetic resonance (NMR) spectroscopy and infrared (IR) absorption spectroscopy, with the data shown below.

¹H-NMR: CDCl₃ (ppm)

-   -   2.37 (3H, s, Ha)     -   6.09-6.11 (1H, d, Hf)     -   6.88-6.90 (1H, d, Hg)     -   7.20-7.36 (4H, m, Hb, Hc, Hd, He)     -   9.23 (1H, s, Hh)

IR: cm⁻¹

-   -   3253, 3075, 3016, 2958, 2825, 2208, 1540, 1521, 1483, 1456,         1423, 1386, 1330, 1290, 1257, 1232, 1101, 1068, 1012, 991, 844,         798, 763, 734, 723, 692, 678, 644

Synthesis Example 15 Synthesis of (3-(4-(4-methylphenylsulfonyloxy)phenylsulfonyloxy)imino-3H-thiophen-2-ylidene)-(2-methylphenyl)acetonitrile

In 490 g of tetrahydrofuran were dissolved 45 g (0.19 mol) of (3-(hydroxy)imino-3H-thiophen-2-ylidene)-(2-methylphenyl)-acetonitrile in Synthesis Example 14 and 61.8 g (0.19 mol) of 4-(4′-methylphenylsulfonyloxy)benzenesulfonyl chloride in Synthesis Example 7. To the solution cooled, 20.6 g (0.20 mol) of triethylamine was added dropwise such that the temperature might not exceed 10° C. The solution was allowed to ripen for 1 hour at room temperature, after which 150 g of water and 500 g of dichloromethane were added. The organic layer was separated, and washed with 150 g of water three times. The organic layer was concentrated in vacuum to 130 g. Methanol was added to the concentrate for recrystallization, followed by filtration and drying. There was obtained 83 g of yellow crystals. The crystals were purified by silica gel column chromatography (eluent, dichloromethane). The elute was concentrated, followed by recrystallization from methanol, filtration and drying. There was obtained 77 g of yellow crystals (yield 72%).

The compound was analyzed by NMR and IR spectroscopy, with the data shown below.

¹H-NMR: CDCl₃ (ppm)

-   -   2.32 (3H, s, Ha)     -   2.46 (3H, s, Hl)     -   6.09-6.11 (1H, d, Hg or Hf)     -   6.78-6.80 (1H, d, Hf or Hg)     -   7.15-7.38 (8H, m, Hi, Hk, Hb, Hc, Hd, He)     -   7.71-7.73 (2H, d, Hj)     -   8.15-8.18 (2H, d, Hh)

IR: cm⁻¹

-   -   2202, 1733, 1587, 1525, 1487, 1456, 1405, 1383, 1296, 1261,         1236, 1195, 1178, 1157, 1120, 1092, 1041, 1016, 852, 816, 793,         754, 731, 706, 677, 650, 625, 609, 586, 563, 549, 444

Synthesis Examples 16-21

The target compounds shown below were synthesized by the same procedures as in Synthesis Examples 14 and 15 except that the sulfonyl chlorides of Synthesis Examples 8 to 13 were used instead of the 4-(4′-methylphenylsulfonyloxy)benzenesulfonyl chloride in Synthesis Example 15.

Synthesis Example 16 (3-(2,5-bis(4-methylphenylsulfonyloxy)benzenesulfonyloxy)imino-3H-thiophen-2-ylidene)-(2-methylphenyl)acetonitrile Synthesis Example 17 (3-(6-(4-methylphenylsulfonyloxy)naphthalene-2-sulfonyloxy)imino-3H-thiophen-2-ylidene)-(2-methylphenyl)-acetonitrile Synthesis Example 18 (3-(4-(4-methylphenylsulfonyloxy)naphthalene-1-sulfonyloxy)imino-3H-thiophen-2-ylidene)-(2-methylphenyl)-acetonitrile Synthesis Example 19 (3-(8-(4-methylphenylsulfonyloxy)naphthalene-1-sulfonyloxy)imino-3H-thiophen-2-ylidene)-(2-methylphenyl)-acetonitrile Synthesis Example 20 (3-(3-methoxy-4-(4-methylphenylsulfonyloxy)benzenesulfonyloxy)imino-3H-thiophen-2-ylidene)-(2-methylphenyl)-acetonitrile Synthesis Example 21 (3-(3-methyl-4-(4-methylphenylsulfonyloxy)benzenesulfonyloxy)imino-3H-thiophen-2-ylidene)-(2-methylphenyl)-acetonitrile Examples 1-9 and Comparative Examples 1-3

Resist materials were prepared in accordance with the formulation shown in Table 1. The components used are shown below.

-   Polymer A: p-hydroxystyrene/p-1,1-dimethylethoxy-styrene copolymer     having a compositional ratio (molar ratio) of 70:30 and a Mw of     10,000 -   Polymer B: p-hydroxystyrene/p-1,1-dimethylpropoxy-styrene copolymer     having a compositional ratio (molar ratio) of 70:30 and a Mw of     10,000 -   Polymer C:     p-hydroxystyrene/p-1,1-dimethylethoxy-styrene/2-ethyl-2-adamantyl     acrylate copolymer having a compositional ratio (molar ratio) of     70:20:10 and a Mw of 15,000 -   Polymer D:     p-hydroxystyrene/p-1,1-dimethylpropoxy-styrene/1-ethyl-1-norbornene     methacrylate copolymer having a compositional ratio (molar ratio) of     75:20:5 and a Mw of 15,000 -   Polymer E: p-hydroxystyrene/p-1,1-dimethylpropoxy-styrene/tert-butyl     acrylate copolymer having a compositional ratio (molar ratio) of     70:25:5 and a Mw of 15,000 -   Polymer F:     p-hydroxystyrene/p-1,1-dimethylpropoxy-styrene/1-ethylcyclopentyl     methacrylate copolymer having a compositional ratio (molar ratio) of     75:20:5 and a Mw of 15,000 -   Polymer G:     p-hydroxystyrene/p-1,1-dimethylpropoxy-styrene/1-ethylcyclopentyl     methacrylate/indene copolymer having a compositional ratio (molar     ratio) of 75:10:8:7 and a Mw of 12,000 -   Polymer H: poly(p-hydroxystyrene) in which hydroxyl groups are     protected with 30 mol % of 1-ethoxyethyl groups, having a Mw of     12,000 -   PAG1: compound of Synthesis Example 15 -   PAG2: compound of Synthesis Example 16 -   PAG3: compound of Synthesis Example 17 -   PAG4: triphenylsulfonium nonafluoro-1-butanesulfonate -   PAG5: (4-tert-butoxyphenyl)diphenylsulfonium 10-camphorsulfonate -   PAG6: triphenylsulfonium 4-(4-toluenesulfonyl)oxybenzenesulfonate -   PAG7: bis(cyclohexylsulfonyl)diazomethane -   PAG8:     (5-(10-camphorsulfonyloxy)imino-5H-thiophen-2-ylidene)-(2-methylphenyl)acetonitrile -   PAG9:     (5-(4-toluenesulfonyloxy)imino-5H-thiphen-2-ylidene)-(2-methylphenyl)-acetonitrile -   Basic compound A: tri-n-butylamine -   Basic compound B: tris(2-methoxyethyl)amine -   Organic acid derivative A: 4,4-bis(4′-hydroxyphenyl)valeric acid -   Thermal flow regulator: Emulgen MS-110 (Kao Corp.) -   Surfactant A: FC-430 (Sumitomo 3M Co., Ltd.) -   Surfactant B: Surflon S-381 (Asahi Glass Co., Ltd.) -   Organic solvent A: propylene glycol methyl ether acetate -   Organic solvent B: ethyl lactate

TABLE 1 Comparative Example Example Composition (pbw) 1 2 3 4 5 6 7 8 9 1 2 3 Polymer A 80 40 80 40 Polymer B 80 40 Polymer C 80 40 Polymer D 80 Polymer E 80 Polymer F 80 Polymer G 80 40 Polymer H 40 80 PAG1 1 1 1 1 1 0.5 1 1 PAG2 1 PAG3 0.5 PAG4 1 1 1 1 PAG5 1 1 1 1 1 1 2 PAG6 1 2 1 1 PAG7 2 1 2 1 1 2 4 2 2 PAG8 0.5 PAG9 1 1 Basic compound A 0.3 0.3 0.3 0.3 0.3 0.3 0.15 0.3 0.3 Basic compound B 0.3 0.3 0.3 0.15 Thermal flow 1 1 1 1 regulator Organic acid 0.5 0.5 derivative A Surfactant A 0.25 0.25 0.25 0.25 0.25 0.25 Surfactant B 0.25 0.25 0.25 0.25 0.25 0.25 Solvent A 385 385 385 280 385 385 385 385 385 280 382 385 Solvent B 105 105

The resist materials thus obtained were each filtered through a 0.2-μm Teflon® filter, thereby giving resist solutions. These resist solutions were spin-coated onto 8-inch silicon wafers having an organic antireflection film (Brewer Science, DUV-44) of 610 Å thick coated thereon, so as to give a dry thickness of 0.4 μm. For the coating and subsequent baking and developing steps, a coater/developer Clean Track Act 8 by Tokyo Electron Ltd. was used.

The coated wafer was then baked on a hot plate at 110° C. for 90 seconds. The resist films were exposed to 2/3 annular illumination using an excimer laser scanner NSR-S203B (Nikon Corp., NA 0.68), then baked (PEB) at 110° C. for 90 seconds, and developed with a solution of 2.38% tetramethylammonium hydroxide in water, thereby giving positive patterns (Examples 1-9 and Comparative Examples 1-3).

The resulting resist patterns were evaluated as described below.

Resist Pattern Evaluation

The optimum exposure dose (sensitivity Eop) was the exposure dose which provided a 1:1 resolution at the top and bottom of a 0.16-μm densely packed contact hole pattern. The minimum hole size (μm) of a contact hole pattern which was ascertained separate at this dose was the resolution of a test resist. The shape in cross section of the resolved resist pattern was examined under a scanning electron microscope (SEM). The depth of focus (DOF) was determined by offsetting the focal point and judging the resist to be satisfactory when the resist pattern shape was kept rectangular and the resist pattern film thickness was kept above 80% of that at accurate focusing.

A top loss resulting from a resist top portion being dissolved away was determined by observing the 0.16-μm dense contact hole pattern under a top-down SEM and inspecting a white ring in the periphery of a hole (observable as a film thickness change in the periphery of a hole). A sample with no white ring observed is judged acceptable (OK) and a sample with white rings observed is unacceptable (NG).

The resolution of a resist was also determined with respect to a 0.20-μm isolated (1:5) hole pattern. The 0.20-μm isolated (1:5) hole pattern was produced while exposing at the optimum dose for resolution of the 0.16-μm dense contact hole pattern and shifting the focal depth by −0.2 μm. The shape in cross section of the resolved resist pattern was examined under a SEM. A pattern which has been resolved to the bottom of holes is judged acceptable (OK).

The PED stability of a resist was evaluated with respect to a 0.16-μm dense contact hole pattern by effecting post-exposure bake (PEB) after 24 hours of holding from exposure at the optimum dose and determining a variation of 0.16-μm hole size. A less variation value indicates greater PED stability.

For examining the level of standing waves, a resist pattern was similarly produced except that the resist solution was spin coated onto a 8-inch silicon wafer (bare silicon) to a thickness of 0.4 μm. The optimum exposure dose (sensitivity Eop) was the exposure dose which provided a 1:1 resolution at the top and bottom of a 0.18-μm dense contact hole pattern (differring from the optimum dose for 0.16 μm). The shape in cross section of the resist pattern resolved at this optimum dose was observed under a SEM and visually determined. A sample with no standing waves observable is judged acceptable (OK) while a sample with standing waves observable is unacceptable (NG).

The results of resist pattern evaluation are shown in Table 2.

TABLE 2 0.16-μm Resolution 24-hr PED pattern Resist of dimensional Sensitivity Resolution Profile DOF top isolated stability Standing (mJ/cm²) (μm) shape (μm) shape pattern (nm) waves Example 1 70 0.15 rectangular 1.0 OK OK 0 OK Example 2 75 0.15 rectangular 1.0 OK OK 0 OK Example 3 73 0.15 rectangular 0.8 OK OK 0 OK Example 4 73 0.15 rectangular 0.8 OK OK 0 OK Example 5 70 0.15 rectangular 1.0 OK OK 0 OK Example 6 75 0.15 rectangular 1.0 OK OK 0 OK Example 7 73 0.15 rectangular 0.8 OK OK 0 OK Example 8 73 0.15 rectangular 0.8 OK OK 0 OK Example 9 70 0.15 rectangular 0.8 OK OK 0 OK Comparative 75 0.15 rectangular 0.8 OK NG 0 OK Example 1 Comparative 70 0.15 rounded top 0.8 NG NG 4 NG Example 2 Comparative 73 0.15 rounded top 0.8 NG OK 10 NG Example 3

Other Evaluation

The solubility of resist material in a solvent mixture was examined by visual observation and in terms of clogging upon filtration.

With respect to the applicability of a resist solution, uneven coating was visually observed. Additionally, using a thickness gage Lambda Ace VM-3010 (optical interference thickness gage by Dainippon Screen Mfg. Co., Ltd.), the thickness of a resist film on a common wafer was measured at different positions, based on which a variation from the desired coating thickness (0.6 μm) was calculated. The applicability was rated “good” when the variation was within 0.5% (that is, within 0.003 μm), “fair” when the variation was from more than 0.5% to 1%, and “poor” when the variation was more than 1%.

Storage stability was judged in terms of foreign matter precipitation or sensitivity change with the passage of time. After the resist solution was aged for 100 days at the longest, the number of particles of greater than 0.3 μm per ml of the resist solution was counted by means of a particle counter KL-20A (Rion Co., Ltd.), and the foreign matter precipitation was determined “good” when the number of particles is not more than 5. Also, the sensitivity change was rated “good” when a change with time of sensitivity (Eop) was within 5% from that immediately after preparation. Samples outside the ranges are rated “poor”.

The results are shown in Table 3.

TABLE 3 Storage Solubility Applicability stability Example 1 good good good Example 2 good good good Example 3 good good good Example 4 good good good Example 5 good good good Example 6 good good good Example 7 good good good Example 8 good good good Example 9 good good good Comparative Example 1 good good good Comparative Example 2 good good good Comparative Example 3 good good good

Further, the compositions of Examples 1, 2 and 6 and Comparative Example 1 were examined for thermal flow by the following procedure. The results are shown in Table 4.

Thermal Flow Test

The optimum exposure dose (sensitivity Eop) was the exposure dose which provided a 1:1 resolution at the top and bottom of a 0.16-μm dense contact hole pattern. The contact hole pattern which was ascertained separate at this dose was heated on a hot plate at 150° C. for 100 seconds to cause the resist to flow for reducing the hole pattern to a size of 0.10 μm. A sample wherein a hole pattern size variation in the wafer plane falls within ±10% is judged good while a sample with a hole pattern size variation in excess of ±10% is poor.

TABLE 4 Thermal flow Example 1 good Example 2 good Example 6 good Comparative Example 1 poor

Japanese Patent Application No. 2006-160575 is incorporated herein by reference.

Although some preferred embodiments have been described, many modifications and variations may be made thereto in light of the above teachings. It is therefore to be understood that the invention may be practiced otherwise than as specifically described without departing from the scope of the appended claims. 

1. A photoacid generator for use in chemically amplified resist compositions, having the general formula (1):

wherein R is independently selected from the class consisting of hydrogen, fluorine, chlorine atoms, nitro groups, and substituted or unsubstituted, straight, branched or cyclic alkyl and alkoxy groups of 1 to 12 carbon atoms, n is 0 or 1, m is 1 or 2, r is an integer of 0 to 4, and r′ is an integer of 0 to
 5. 2. A photoacid generator for use in chemically amplified resist compositions, having the formula (1a):


3. A chemically amplified resist composition comprising (A) a resin which changes its solubility in an alkaline developer under the action of an acid, and (B) the photoacid generator of claim
 1. 4. A chemically amplified positive resist composition comprising (A) a resin which changes its solubility in an alkaline developer under the action of an acid, and (B) the photoacid generator of claim
 1. 5. The resist composition of claim 3, further comprising (C) a compound capable of generating an acid upon exposure to radiation, other than component (B).
 6. The resist composition of claim 3 wherein the resin (A) has such substituent groups having C—O—C linkages that the solubility in an alkaline developer changes as a result of scission of the C—O—C linkages under the action of an acid.
 7. The resist composition of claim 6 wherein the resin (A) is a polymer containing phenolic hydroxyl groups in which hydrogen atoms of the phenolic hydroxyl groups are substituted with acid labile groups of one or more types in a proportion of more than 0 mol % to 80 mol % on the average of the entire hydrogen atoms of the phenolic hydroxyl groups, the polymer having a weight average molecular weight of 3,000 to 100,000.
 8. The resist composition of claim 6 wherein the resin (A) is a polymer comprising recurring units of the following general formula (2a):

wherein R¹ is hydrogen or methyl, R² is a straight, branched or cyclic alkyl group of 1 to 8 carbon atoms, x is 0 or a positive integer, y is a positive integer, satisfying x+y≦5, R³ is an acid labile group, S and T are positive integers, satisfying 0<T/(S+T)≦0.8, wherein the polymer contains units in which hydrogen atoms of phenolic hydroxyl groups are partially substituted with acid labile groups of one or more types, a proportion of the acid labile group-bearing units is on the average from more than 0 mol % to 80 mol % based on the entire polymer, and the polymer has a weight average molecular weight of 3,000 to 100,000.
 9. The resist composition of claim 6 wherein the resin (A) is a polymer comprising recurring units of the following general formula (2a′):

wherein R¹ is hydrogen or methyl, R² is a straight, branched or cyclic alkyl group of 1 to 8 carbon atoms, R³ is an acid labile group, R^(3a) is hydrogen or an acid labile group, at least some of R^(3a) being acid labile groups, x is 0 or a positive integer, y is a positive integer, satisfying x+y≦5, M and N are positive integers, L is 0 or a positive integer, satisfying 0<N/(M+N+L)≦0.5 and 0<(N+L)/(M+N+L)≦0.8, wherein the polymer contains on the average from more than 0 mol % to 50 mol % of those units derived from acrylate and methacrylate, and also contains on the average from more than 0 mol % to 80 mol % of acid labile group-bearing units, based on the entire polymer, and the polymer has a weight average molecular weight of 3,000 to 100,000.
 10. The resist composition of claim 6 wherein the resin (A) is a polymer comprising recurring units of the following general formula (2a″):

wherein R¹ is hydrogen or methyl, R² is a straight, branched or cyclic alkyl group of 1 to 8 carbon atoms, R³ is an acid labile group, R^(3a) is hydrogen or an acid labile group, at least some of R^(3a) being acid labile groups, x is 0 or a positive integer, y is a positive integer, satisfying x+y≦5, yy is 0 or a positive integer, satisfying x+yy≦4, A and B are positive integers, C, D and E each are 0 or a positive integer, satisfying 0<(B+E)/(A+B+C+D+E)≦0.5 and 0<(C+D+E)/(A+B+C+D+E)≦0.8, wherein the polymer contains on the average from more than 0 mol % to 50 mol % of those units derived from indene and/or substituted indene, and also contains on the average from more than 0 mol % to 80 mol % of acid labile group-bearing units, based on the entire polymer, and the polymer has a weight average molecular weight of 3,000 to 100,000.
 11. The resist composition of claim 6 wherein the acid labile group is a tertiary alkyl group of 4 to 20 carbon atoms or a group of the following general formula (5):

wherein R⁸ is a straight, branched or cyclic alkyl group of 1 to 8 carbon atoms or an aryl group of 6 to 20 carbon atoms which may be substituted, h is 0 or 1, i is 0, 1, 2 or 3, satisfying 2h+i=2 or
 3. 12. The resist composition of claim 3, further comprising (D) a basic compound.
 13. The resist composition of claim 3, further comprising (E) an organic acid derivative.
 14. The resist composition of claim 3, further comprising (F) an organic solvent which is a propylene glycol alkyl ether acetate, an alkyl lactate or a mixture thereof.
 15. A process for forming a pattern, comprising the steps of: (i) applying the resist composition of claim 3 onto a substrate to form a coating, (ii) heat treating the coating and exposing the coating to high energy radiation with a wavelength of up to 300 nm or electron beam through a photomask, (iii) optionally heat treating the exposed coating, and developing the coating with a developer.
 16. A process for forming a pattern, comprising the steps of: (i) applying the resist composition of claim 3 onto an inorganic substrate such as a SiON film to form a coating, (ii) heat treating the coating and exposing the coating to high energy radiation with a wavelength of up to 300 nm or electron beam through a photomask, (iii) optionally heat treating the exposed coating, and developing the coating with a developer.
 17. A process for forming a pattern, comprising the steps of: (i) applying the resist composition of claim 3 onto a substrate to form a coating, (ii) heat treating the coating and exposing the coating to high energy radiation with a wavelength of up to 300 nm or electron beam through a photomask, (iii) optionally heat treating the exposed coating, and developing the coating with a developer to form a pattern profile, and (iv) heat treating for causing the pattern profile to flow for thereby reducing its size. 